Script | Spoken-Tutorial - User contributions [en]

Python-3.4.3/C2/Getting-started-with-files/English

2018-01-31T06:39:16Z

Trupti:

'''Title of script''': '''Getting started with files'''

'''Author: Trupti Kini'''

'''Keywords: IPython, files, read, write, append, mode, splitlines()'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''files'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to -
# Open a file.
# Read the contents of the file line by line.
# Read the entire content of the file at once.
# Append the lines of a file to a '''list''' and
# Close the file.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3 '''and
* '''IPython 5.1.0''' 

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know about

* '''Lists''' and
* '''for statement'''

If not, see the pre-requisite '''Python''' tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

Highlight according to narration: (open and file object)

'''''syntax:'''''

'''''file_object <nowiki>= open(</nowiki>filename, mode)'''''

Filename - name of the file to be opened.

Mode - indicates how the file is going to be opened.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To open a file for reading or writing, we can use a '''built in function''' called '''open()'''.

'''Open() function''' returns a '''file object'''.

The syntax is shown here.

'''Filename''' - is the name of the file to be opened.

'''Mode'''- This indicates how the file is going to be opened.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

'''''syntax:'''''

'''''file_object <nowiki>= open(filename, mode)</nowiki>'''''

r- Read mode

w- Write mode

a -Appending mode

r+ - Read and Write
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| r- is for '''Read mode'''

w- is for '''Write mode'''

a - represents '''Appending mode''' and

r+ - for both '''Read and Write mode'''

Specifying '''mode''' is optional.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open pendulum.txt in text editor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us open a file '''pendulum.txt''' in a text editor.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the columns in the file
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This file contains 2 data columns, '''length''' and '''time''' of '''pendulum'''.

We will be using this text file for our demonstration.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Text box on the screen as per the narration
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The file '''pendulum.txt''' is available in the '''Code File link''' of this tutorial.

Please download it in '''Home directory''' and use it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

Press '''Ctrl+Alt+T '''keys

Type '''ipython3'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

Type

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab package'''.

Type '''%pylab '''and press''' Enter.'''

Let us clear the '''terminal'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Open pendulum.txt
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us open the file '''pendulum.txt.'''

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Type

'''f''''' is equal to''''' open''''' inside parentheses inside quotes '''''pendulum '''''dot '''''txt'''

Here the '''mode''' is not specified.

By default, it is '''‘r’'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''f'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us type '''f''' on the '''terminal''' to see what it is.

The '''file object f''' shows the filename and '''mode''' of the file which is open.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''filename '''and '''mode 'r''''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| ''''r' '''stands for '''read only mode'''.

As you can see, this '''file''' is open in '''read only mode'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn to read the whole '''file''' into a single '''variable'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''pend = f.read()'''

Highlight pend= '''f.read()'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type
'''pend '''''equal to '''''f '''''dot '''''read'' '''open and close parentheses.''

We use the '''read method''' to read all the contents of the file into the '''variable pend'''

Press '''Enter'''

To use '''read method''' we use the '''file object dot read method'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''print(pend)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us see what '''pend '''contains, by typing

'''print '''''inside parentheses '''''pend.'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the data
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can see that '''pend''' has all the data of the '''file pendulum.txt'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend'''Highlight data with newline characters
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type just '''pend''' to see more explicitly, what it contains.

We can see the '''newline characters''' as well, in the output.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us learn to split the '''variable pend''' into a '''list''' of lines in the file.

We use the '''method splitlines''' to split a file of data into '''list''' of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend_list = pend.splitlines()'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| For this we need to store this '''list '''in a '''variable''', say '''pend_list'''

Type

'''pend_list '''''equal to''''' pend '''''dot '''''splitlines '''''open and close parentheses''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''pend_list'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
Type '''pend '''''underscore '''''list '''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Highlight the data into list of lines
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We got the data into '''list''' of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the data into list of lines
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''pend_list''' does not contain '''newline characters '''like '''\n'''.

This is because the '''string pend''' is split on the '''newline characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
But, before that we will have to close the file, since the file has already been read till the end.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''f.close()'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us close the '''file''' opened into '''f'''.

Type '''f dot close ''' ''open and close parentheses''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''closed file'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It is a good programming practice
* to '''close''' any '''file objects''' that we have opened
* after their job is done.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video here, try out the following exercise and then resume the video.

Re-open the file '''pendulum.txt''' with '''f''' as the '''file object'''.

Recall that we have closed the file earlier.

Let us switch back to the terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now move on to reading files line- by - line.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type'''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

To re-open the file again, type

'''f '''''is equal to '''''open '''''inside parentheses inside quotes '''''pendulum.txt'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''for line in f:'''

'''print(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, to read the file line-by-line, we '''iterate''' over the '''file object''' using the '''for loop'''.

Let us '''iterate''' over the '''file''' line-wise and '''print''' each of the lines.

Let us clear the '''terminal'''.

Type

'''for line in f colon''' press '''Enter'''

'''four spaces print inside parentheses line'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here, '''line''' is a '''loop variable''', and it is not a '''keyword'''.

We could have used any other '''variable''' name, but '''line''' seems meaningful enough.

Press '''Enter''' twice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Instead of just printing the lines, let us append them into a '''list''', say '''line_list'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''<nowiki>line_list = []</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We first '''initialize''' a '''line_list '''as an '''empty-list'''

Type,

'''line ''underscore ''list ''is'' ''equal to ''open and close square brackets.'''
Press Enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight according to narration.

Type

'''for line in open('pendulum.txt'):'''

'''line_list.append(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type the code as

'''for line in open ''inside parentheses inside quotes ''pendulum ''dot'' txt colon''' press '''Enter'''

'''''four space'' line'' underscore'' list ''dot ''append i''nside parentheses'' line'''

Press '''Enter''' twice.

Here, the '''for loop '''reads the file '''pendulum.txt '''line-by-line.

The '''append method''' will add each of the line to the '''list, line_list.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We could, as usual close the file using '''f.close() '''and re-open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| But, this time, let's leave the '''file object f '''and directly open the file within the '''for statement'''.

This will save us the trouble of closing the file, each time we open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''line_list '''and press '''Enter'''

Highlight data
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us see what '''line_list''' contains.

Type '''line ''underscore '' list '''and press '''Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''newline characters'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''line ''underscore '' list''' is a '''list''' of the lines in the file, along with the '''newline characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can strip out the '''newline characters''' from the lines by using some '''string methods'''.

This will be covered in the further tutorial on '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we learnt to -

* Open and close files using the '''open''' and '''close methods''' respectively.
* Read the data in the files as a whole, by using the '''read method'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

* Read the data in the files line by line by iterating over the '''file object''' using the '''for loop'''.
* Append the lines of a file to a '''list''' using the '''append method''' within the '''for loop'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. The '''open function''' returns a

* '''string'''
* '''list'''
* '''file object'''
* '''function'''

2. What does the '''function splitlines()''' do.

* Displays the data as '''strings''' all in a line
* Displays the data line by line as '''strings'''
* Displays the data line by line but not as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers are,

# '''open function''' returns a '''file object'''
# '''splitlines() '''displays the data line by line as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-files/English

2018-01-29T06:44:38Z

Trupti:

'''Title of script''': '''Getting started with files'''

'''Author: Trupti Kini'''

'''Keywords: IPython, files, read, write, append, mode, splitlines()'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''files'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to -
# Open a file.
# Read the contents of the file line by line.
# Read the entire content of the file at once.
# Append the lines of a file to a '''list''' and
# Close the file.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3 '''and
* '''IPython 5.1.0''' 

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know about

* '''Lists''' and
* '''for statement'''

If not, see the pre-requisite '''Python''' tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

Highlight according to narration: (open and file object)

'''''syntax:'''''

'''''file_object <nowiki>= open(</nowiki>filename, mode)'''''

Filename - name of the file to be opened.

Mode - indicates how the file is going to be opened.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To open a file for reading or writing, we can use a '''built in function''' called '''open()'''.

'''Open() function''' returns a '''file object'''.

The syntax is shown here.

'''Filename''' - is the name of the file to be opened.

'''Mode'''- This indicates how the file is going to be opened.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

'''''syntax:'''''

'''''file_object <nowiki>= open(filename, mode)</nowiki>'''''

r- Read mode

w- Write mode

a -Appending mode

r+ - Read and Write
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| r- is for '''Read mode'''

w- is for '''Write mode'''

a - represents '''Appending mode''' and

r+ - for both '''Read and Write mode'''

Specifying '''mode''' is optional.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open pendulum.txt in text editor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us open a file '''pendulum.txt''' in a text editor.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the columns in the file
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This file contains 2 data columns, '''length''' and '''time''' of '''pendulum'''.

We will be using this text file for our demonstration.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Text box on the screen as per the narration
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The file '''pendulum.txt''' is available in the '''Code File link''' of this tutorial.

Please download it in '''Home directory''' and use it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

Press '''Ctrl+Alt+T '''keys

Type '''ipython3'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

Type

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab package'''.

Type '''%pylab '''and press''' Enter.'''

Let us clear the '''terminal'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Open pendulum.txt
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us open the file '''pendulum.txt.'''

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Type

'''f''''' is equal to''''' open''''' inside parentheses inside quotes '''''pendulum '''''dot '''''txt'''

Here the '''mode''' is not specified.

By default, it is '''‘r’'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''f'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us type '''f''' on the '''terminal''' to see what it is.

The '''file object f''' shows the filename and '''mode''' of the file which is open.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''filename '''and '''mode 'r''''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| ''''r' '''stands for '''read only mode'''.

As you can see, this '''file''' is open in '''read only mode'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn to read the whole '''file''' into a single '''variable'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''pend = f.read()'''

Highlight pend= '''f.read()'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type
'''pend '''''equal to '''''f '''''dot '''''read'' '''open and close parentheses.''

We use the '''read method''' to read all the contents of the file into the '''variable pend'''

Press '''Enter'''

To use '''read method''' we use the '''file object dot read method'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''print(pend)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us see what '''pend '''contains, by typing

'''print '''''inside parentheses '''''pend.'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the data
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can see that '''pend''' has all the data of the '''file pendulum.txt'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend'''Highlight data with newline characters
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type just '''pend''' to see more explicitly, what it contains.

We can see the '''newline characters''' as well, in the output.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us learn to split the '''variable pend''' into a '''list''' of lines in the file.

We use the '''method splitlines''' to split a file of data into '''list''' of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend_list = pend.splitlines()'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| For this we need to store this '''list '''in a '''variable''', say '''pend_list'''

Type

'''pend_list '''''equal to''''' pend '''''dot '''''splitlines '''''open and close parentheses''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''pend_list'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
Type '''pend '''''underscore '''''list '''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Highlight the data into list of lines
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We got the data into '''list''' of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the data into list of lines
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''pend_list''' does not contain '''newline characters '''like '''\n'''.

This is because the '''string pend''' is split on the '''newline characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us learn to read the file line-by-line.

But, before that we will have to close the file, since the file has already been read till the end.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''f.close()'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us close the '''file''' opened into '''f'''.

Type '''f dot close ''' ''open and close parentheses''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''closed file'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It is a good programming practice
* to '''close''' any '''file objects''' that we have opened
* after their job is done.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video here, try out the following exercise and then resume the video.

Re-open the file '''pendulum.txt''' with '''f''' as the '''file object'''.

Recall that we have closed the file earlier.

Let us switch back to the terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now move on to reading files line- by - line.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type'''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

To re-open the file again, type

'''f '''''is equal to '''''open '''''inside parentheses inside quotes '''''pendulum.txt'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''for line in f:'''

'''print(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, to read the file line-by-line, we '''iterate''' over the '''file object''' using the '''for loop'''.

Let us '''iterate''' over the '''file''' line-wise and '''print''' each of the lines.

Let us clear the '''terminal'''.

Type

'''for line in f colon''' press '''Enter'''

'''four spaces print inside parentheses line'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here, '''line''' is a '''loop variable''', and it is not a '''keyword'''.

We could have used any other '''variable''' name, but '''line''' seems meaningful enough.

Press '''Enter''' twice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Instead of just printing the lines, let us append them into a '''list''', say '''line_list'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''<nowiki>line_list = []</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We first '''initialize''' a '''line_list '''as an '''empty-list'''

Type,

'''line ''underscore ''list ''is'' ''equal to ''open and close square brackets.'''
Press Enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight according to narration.

Type

'''for line in open('pendulum.txt'):'''

'''line_list.append(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type the code as

'''for line in open ''inside parentheses inside quotes ''pendulum ''dot'' txt colon''' press '''Enter'''

'''''four space'' line'' underscore'' list ''dot ''append i''nside parentheses'' line'''

Press '''Enter''' twice.

Here, the '''for loop '''reads the file '''pendulum.txt '''line-by-line.

The '''append method''' will add each of the line to the '''list, line_list.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We could, as usual close the file using '''f.close() '''and re-open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| But, this time, let's leave the '''file object f '''and directly open the file within the '''for statement'''.

This will save us the trouble of closing the file, each time we open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''line_list '''and press '''Enter'''

Highlight data
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us see what '''line_list''' contains.

Type '''line ''underscore '' list '''and press '''Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''newline characters'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''line ''underscore '' list''' is a '''list''' of the lines in the file, along with the '''newline characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can strip out the '''newline characters''' from the lines by using some '''string methods'''.

This will be covered in the further tutorial on '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we learnt to -

* Open and close files using the '''open''' and '''close methods''' respectively.
* Read the data in the files as a whole, by using the '''read method'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

* Read the data in the files line by line by iterating over the '''file object''' using the '''for loop'''.
* Append the lines of a file to a '''list''' using the '''append method''' within the '''for loop'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. The '''open function''' returns a

* '''string'''
* '''list'''
* '''file object'''
* '''function'''

2. What does the '''function splitlines()''' do.

* Displays the data as '''strings''' all in a line
* Displays the data line by line as '''strings'''
* Displays the data line by line but not as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers are,

# '''open function''' returns a '''file object'''
# '''splitlines() '''displays the data line by line as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-files/English

2018-01-29T06:35:16Z

Trupti:

'''Title of script''': '''Getting started with files'''

'''Author: Trupti Kini'''

'''Keywords: IPython, files, read, write, append, mode, splitlines()'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''files'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to -
# Open a file.
# Read the contents of the file line by line.
# Read the entire content of the file at once.
# Append the lines of a file to a '''list''' and
# Close the file.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3 '''and
* '''IPython 5.1.0''' 

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know about

* '''Lists''' and
* '''for statement'''

If not, see the pre-requisite '''Python''' tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

Highlight according to narration: (open and file object)

'''''syntax:'''''

'''''file_object <nowiki>= open(</nowiki>filename, mode)'''''

Filename - name of the file to be opened.

Mode - indicates how the file is going to be opened.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To open a file for reading or writing, we can use a '''built in function''' called '''open()'''.

'''Open() function''' returns a '''file object'''.

The syntax is shown here.

'''Filename''' - is the name of the file to be opened.

'''Mode'''- This indicates how the file is going to be opened.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

'''''syntax:'''''

'''''file_object <nowiki>= open(filename, mode)</nowiki>'''''

r- Read mode

w- Write mode

a -Appending mode

r+ - Read and Write
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| r- is for '''Read mode'''

w- is for '''Write mode'''

a - represents '''Appending mode''' and

r+ - for both '''Read and Write mode'''

Specifying '''mode''' is optional.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open pendulum.txt in text editor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us open a file '''pendulum.txt''' in a text editor.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the columns in the file
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This file contains 2 data columns, '''length''' and '''time''' of '''pendulum'''.

We will be using this text file for our demonstration.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Text box on the screen as per the narration
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The file '''pendulum.txt''' is available in the '''Code File link''' of this tutorial.

Please download it in '''Home directory''' and use it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

Press '''Ctrl+Alt+T '''keys

Type '''ipython3'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

Type

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab package'''.

Type '''%pylab '''and press''' Enter.'''

Let us clear the '''terminal'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Open pendulum.txt
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us open the file '''pendulum.txt.'''

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Type

'''f''''' is equal to''''' open''''' inside parentheses inside quotes '''''pendulum '''''dot '''''txt'''

Here the '''mode''' is not specified.

By default, it is '''‘r’'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''f'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us type '''f''' on the '''terminal''' to see what it is.

The '''file object f''' shows the filename and '''mode''' of the file which is open.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''filename '''and '''mode 'r''''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| ''''r' '''stands for '''read only mode'''.

As you can see, this '''file''' is open in '''read only mode'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn to read the whole '''file''' into a single '''variable'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''pend = f.read()'''

Highlight pend= '''f.read()'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type
'''pend '''''equal to '''''f '''''dot '''''read'' '''open and close parentheses.''

We use the '''read method''' to read all the contents of the file into the '''variable pend'''

Press '''Enter'''

To use '''read method''' we use the '''file object dot read method'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''print(pend)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us see what '''pend '''contains, by typing

'''print '''''inside parentheses '''''pend.'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the data
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can see that '''pend''' has all the data of the '''file pendulum.txt'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend'''Highlight data with newline characters
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type just '''pend''' to see more explicitly, what it contains.

We can see the '''newline characters''' as well, in the output.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us learn to split the '''variable pend''' into a '''list''' of lines in the file.

We use the '''method splitlines''' to split a file of data into '''list''' of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend_list = pend.splitlines()'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| For this we need to store this '''list '''in a '''variable''', say '''pend_list'''

Type

'''pend_list '''''equal to''''' pend '''''dot '''''splitlines '''''open and close parentheses''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''pend_list'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
Type '''pend '''''underscore '''''list '''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Highlight the data into list of lines
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We got the data into '''list''' of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the data into list of lines
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''pend_list''' does not contain '''newline characters '''like '''\n'''.

This is because the '''string pend''' is split on the '''newline characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us learn to read the file line-by-line.

But, before that we will have to close the file, since the file has already been read till the end.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''f.close()'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us close the '''file''' opened into '''f'''.

Type '''f dot close ''' ''open and close parentheses''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''closed file'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It is a good programming practice
* to '''close''' any '''file objects''' that we have opened
* after their job is done.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video here, try out the following exercise and then resume the video.

Re-open the file '''pendulum.txt''' with '''f''' as the '''file object'''.

Recall that we have closed the file earlier.

Let us switch back to the terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now move on to reading files line- by - line.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type'''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

To re-open the file again, type

'''f '''''is equal to '''''open '''''inside parentheses inside quotes '''''pendulum.txt'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''for line in f:'''

'''print(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, to read the file line-by-line, we '''iterate''' over the '''file object''' using the '''for loop'''.

Let us '''iterate''' over the '''file''' line-wise and '''print''' each of the lines.

Let us clear the '''terminal'''.

Type

'''for line in f colon''' press '''Enter'''

'''four spaces print inside parentheses line'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here, '''line''' is a '''loop variable''', and it is not a '''keyword'''.

We could have used any other '''variable''' name, but '''line''' seems meaningful enough.

Press '''Enter''' twice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Instead of just printing the lines, let us append them into a '''list''', say '''line_list'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''<nowiki>line_list = []</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We first '''initialize''' a '''line_list '''as an '''empty-list'''

Type,

'''line ''underscore ''list ''is'' ''equal to ''open and close square brackets.'''
Press Enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight according to narration.

Type

'''for line in open('pendulum.txt'):'''

'''line_list.append(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type the code as

'''for line in open ''inside parentheses inside quotes ''pendulum ''dot'' txt colon''' press '''Enter'''

'''''four space'' line'' underscore'' list ''dot ''append i''nside parentheses'' line'''

Press '''Enter''' twice.

Here, the '''for loop '''reads the file '''pendulum.txt '''line-by-line.

The '''append method''' will add each of the line to the '''list, line_list.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We could, as usual close the file using '''f.close() '''and re-open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| But, this time, let's leave the '''file object f '''and directly open the file within the '''for statement'''.

This will save us the trouble of closing the file, each time we open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''line_list '''and press '''Enter'''

Highlight data
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us see what '''line_list''' contains.

Type '''line ''underscore '' list '''and press '''Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''newline characters'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''line ''underscore '' list''' is a '''list''' of the lines in the file, along with the '''newline characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can strip out the '''newline characters''' from the lines by using some '''string methods'''.

This will be covered in the further tutorial on '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we learnt to -

# Open and close files using the '''open''' and '''close methods''' respectively.
# Read the data in the files as a whole, by using the '''read method'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

# Read the data in the files line by line by iterating over the '''file object''' using the '''for loop'''.
# Append the lines of a file to a '''list''' using the '''append method''' within the '''for loop'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. The '''open function''' returns a

* '''string'''
* '''list'''
* '''file object'''
* '''function'''

2. What does the '''function splitlines()''' do.

* Displays the data as '''strings''' all in a line
* Displays the data line by line as '''strings'''
* Displays the data line by line but not as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers are,

# '''open function''' returns a '''file object'''
# '''splitlines() '''displays the data line by line as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-files/English

2018-01-29T06:12:47Z

Trupti:

'''Title of script''': '''Getting started with files'''

'''Author: Trupti Kini'''

'''Keywords: IPython, files, read, write, append, mode, splitlines()'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''files'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to -
# Open a file.
# Read the contents of the file line by line.
# Read the entire content of the file at once.
# Append the lines of a file to a '''list''' and
# Close the file.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3 '''and
* '''IPython 5.1.0''' 

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know about

* '''Lists''' and
* '''for statement'''

If not, see the pre-requisite '''Python''' tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

Highlight according to narration: (open and file object)

'''''syntax:'''''

'''''file_object <nowiki>= open(</nowiki>filename, mode)'''''

Filename - name of the file to be opened.

Mode - indicates how the file is going to be opened.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To open a file for reading or writing, we can use a '''built in function''' called '''open()'''.

'''Open() function''' returns a '''file object'''.

The syntax is shown here.

'''Filename''' - is the name of the file to be opened.

'''Mode'''- This indicates how the file is going to be opened.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

'''''syntax:'''''

'''''file_object <nowiki>= open(filename, mode)</nowiki>'''''

r- Read mode

w- Write mode

a -Appending mode

r+ - Read and Write
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| r- is for '''Read mode'''

w- is for '''Write mode'''

a - represents '''Appending mode''' and

r+ - for both '''Read and Write mode'''

Specifying '''mode''' is optional.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open pendulum.txt in text editor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us open a file '''pendulum.txt''' in a text editor.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the columns in the file
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This file contains 2 data columns, '''length''' and '''time''' of '''pendulum'''.

We will be using this text file for our demonstration.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Text box on the screen as per the narration
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The file '''pendulum.txt''' is available in the '''Code File link''' of this tutorial.

Please download it in '''Home directory''' and use it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

Press '''Ctrl+Alt+T '''keys

Type '''ipython3'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

Type

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab package'''.

Type '''%pylab '''and press''' Enter.'''

Let us clear the '''terminal'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Open pendulum.txt
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us open the file '''pendulum.txt.'''

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Type

'''f''''' is equal to''''' open''''' inside parentheses inside quotes '''''pendulum '''''dot '''''txt'''

Here the '''mode''' is not specified.

By default, it is '''‘r’'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''f'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us type '''f''' on the '''terminal''' to see what it is.

The '''file object f''' shows the filename and '''mode''' of the file which is open.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''filename '''and '''mode 'r''''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| ''''r' '''stands for '''read only mode'''.

As you can see, this '''file''' is open in '''read only mode'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn to read the whole '''file''' into a single '''variable'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''pend = f.read()'''

Highlight pend= '''f.read()'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type
'''pend '''''equal to '''''f '''''dot '''''read'' '''open and close parentheses.''

We use the '''read method''' to read all the contents of the file into the '''variable pend'''

Press '''Enter'''

To use '''read method''' we use the '''file object dot read method'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''print(pend)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us see what '''pend '''contains, by typing

'''print '''''inside parentheses '''''pend.'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the data
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can see that '''pend''' has all the data of the '''file pendulum.txt'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend'''Highlight data with newline characters
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type just '''pend''' to see more explicitly, what it contains.

We can see the '''newline characters''' as well, in the output.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us learn to split the '''variable pend''' into a '''list''' of lines in the file.

We use the '''method splitlines''' to split a file of data into '''list''' of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend_list = pend.splitlines()'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| For this we need to store this '''list '''in a '''variable''', say '''pend_list'''

Type

'''pend_list '''''equal to''''' pend '''''dot '''''splitlines '''''open and close parentheses''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''pend_list'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
Type '''pend '''''underscore '''''list '''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Highlight the data into list of lines
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We got the data into '''list''' of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the data into list of lines
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''pend_list''' does not contain '''newline characters '''like '''\n'''.

This is because the '''string pend''' is split on the '''newline characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us learn to read the file line-by-line.

But, before that we will have to close the file, since the file has already been read till the end.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''f.close()'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us close the '''file''' opened into '''f'''.

Type '''f dot close ''' ''open and close parentheses''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''closed file'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It is a good programming practice
* to '''close''' any '''file objects''' that we have opened
* after their job is done.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video here, try out the following exercise and then resume the video.

Re-open the file '''pendulum.txt''' with '''f''' as the '''file object'''.

Recall that we have closed the file earlier.

Let us switch back to the terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now move on to reading files line- by - line.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type'''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

To re-open the file again, type

'''f '''''is equal to '''''open '''''inside parentheses inside quotes '''''pendulum.txt'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''for line in f:'''

'''print(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, to read the file line-by-line, we '''iterate''' over the '''file object''' using the '''for loop'''.

Let us '''iterate''' over the '''file''' line-wise and '''print''' each of the lines.

Let us clear the '''terminal'''.

Type

'''for line in f colon''' press '''Enter'''

'''four spaces print inside parentheses line'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here, '''line''' is a '''loop variable''', and it is not a '''keyword'''.

We could have used any other '''variable''' name, but '''line''' seems meaningful enough.

Press '''Enter''' twice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Instead of just printing the lines, let us append them into a '''list''', say '''line_list'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''<nowiki>line_list = []</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We first '''initialize''' '''line_list '''as an '''empty-list'''

Type,

'''line ''underscore ''list ''is'' ''equal to ''open and close square brackets.'''
Press Enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight according to narration.

Type

'''for line in open('pendulum.txt'):'''

'''line_list.append(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type the code as

'''for line in open ''inside parentheses inside quotes ''pendulum ''dot'' txt colon''' press '''Enter'''

'''''four space'' line'' underscore'' list ''dot ''append i''nside parentheses'' line'''

Press '''Enter''' twice.

Here, the '''for loop '''reads the file '''pendulum.txt '''line-by-line.

The '''append method''' will add each of the line to the '''list, line_list.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We could, as usual close the file using '''f.close() '''and re-open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| But, this time, let's leave the '''file object f '''and directly open the file within the '''for statement'''.

This will save us the trouble of closing the file, each time we open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''line_list '''and press '''Enter'''

Highlight data
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us see what '''line_list''' contains.

Type '''line ''underscore '' list '''and press '''Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''newline characters'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''line ''underscore '' list''' is a '''list''' of the lines in the file, along with the '''newline characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can strip out the '''newline characters''' from the lines by using some '''string methods'''.

This will be covered in the further tutorial on '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we learnt to -

# Open and close files using the '''open''' and '''close methods''' respectively.
# Read the data in the files as a whole, by using the '''read method'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

# Read the data in the files line by line by iterating over the '''file object''' using the '''for loop'''.
# Append the lines of a file to a '''list''' using the '''append method''' within the '''for loop'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. The '''open function''' returns a

* '''string'''
* '''list'''
* '''file object'''
* '''function'''

2. What does the '''function splitlines()''' do.

* Displays the data as '''strings''' all in a line
* Displays the data line by line as '''strings'''
* Displays the data line by line but not as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers are,

# '''open function''' returns a '''file object'''
# '''splitlines() '''displays the data line by line as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2018-01-22T10:44:07Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3''' and
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within '''single/ double/ triple quotes '''is''' '''a''' string.'''

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x ''is equal to''' inside quotes'' '''Hello'''

Press '''Enter'''

'''y ''is equal to''' inside quotes'' '''World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.'''''

Press '''Enter'''

'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''Hello, World!'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

Type '''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight '''HelloHelloHelloHelloHello'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type,

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages'''

Press '''Enter'''

'''print''' ''inside parentheses '' '''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual '''elements''' in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>Type a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

Recall '''a.'''

Press '''Enter'''.

Type,

'''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>Type a[-1] </nowiki>'''

'''<nowiki>Type a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>Type

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''.

Type

'''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''

Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''
Type

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the '''terminal'''.

Recall '''x'''

Press '''Enter'''

Let us manipulate '''x.'''

'''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of '''x[0]''' is '''‘H’'''.

Now we are trying to assign another value '''‘B’''' to '''x[0]'''.

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide '''split()''' and''' join()''' functions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str ''dot join''' inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”

seq = ("a", "b", "c")

print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''

Type

'''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''

'''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

'''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''a-b-c'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined '''a, b, c''' with '''hyphen'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str dot split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''

Type as shown press '''Enter'''

'''print str dot split''' ''open and close parentheses'' press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''['Line1-abcdef', 'Line2-abc', 'Line4-abcd']'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the strings at '''spaces'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly and
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the string ’ is called the apostrophe, to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are strings and r is integer.

s=Hello

t=World

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the string ’ is called the apostrophe, to variable s
# How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'.
# The variables '''s''' and '''t''' are strings and '''r''' is integer.

They are assigned with the values as shown below,
What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value
# The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2018-01-22T10:35:07Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3''' and
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x ''is equal to''' inside quotes'' '''Hello'''

Press '''Enter'''

'''y ''is equal to''' inside quotes'' '''World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.'''''

Press '''Enter'''

'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''Hello, World!'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

Type '''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight '''HelloHelloHelloHelloHello'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type,

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages'''

Press '''Enter'''

'''print''' ''inside parentheses '' '''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual '''elements''' in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>Type a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

Recall '''a.'''

Press '''Enter'''.

Type,

'''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>Type a[-1] </nowiki>'''

'''<nowiki>Type a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>Type

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''.

Type

'''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''

Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''
Type

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the '''terminal'''.

Recall '''x'''

Press '''Enter'''

Let us manipulate '''x.'''

'''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of '''x[0]''' is '''‘H’'''.

Now we are trying to assign another value '''‘B’''' to '''x[0]'''.

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide '''split()''' and''' join()''' functions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str ''dot join''' inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”

seq = ("a", "b", "c")

print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''

Type

'''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''

'''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

'''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''a-b-c'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined '''a, b, c''' with '''hyphen'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str dot split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''

Type as shown press '''Enter'''

'''print str dot split''' ''open and close parentheses'' press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''['Line1-abcdef', 'Line2-abc', 'Line4-abcd']'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the strings at '''spaces'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly and
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the string ’ is called the apostrophe, to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are strings and r is integer.

s=Hello

t=World

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the string ’ is called the apostrophe, to variable s
# How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'.
# The variables '''s''' and '''t''' are strings and '''r''' is integer.

They are assigned with the values as shown below,
What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value
# The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2018-01-22T10:32:10Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3''' and
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x ''is equal to''' inside quotes'' '''Hello'''

Press '''Enter'''

'''y ''is equal to''' inside quotes'' '''World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.'''''

Press '''Enter'''

'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''Hello, World!'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

Type '''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight '''HelloHelloHelloHelloHello'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type,

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages'''

Press '''Enter'''

'''print''' ''inside parentheses '' '''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual '''elements''' in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>Type a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

Recall '''a.'''

Press '''Enter'''.

Type,

'''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>Type a[-1] </nowiki>'''

'''<nowiki>Type a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>Type

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''.

Type

'''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''

Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''
Type

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the '''terminal'''.

Recall '''x'''

Press '''Enter'''

Let us manipulate '''x.'''

'''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of '''x[0]''' is '''‘H’'''.

Now we are trying to assign another value '''‘B’''' to '''x[0]'''.

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide '''split()''' and''' join()''' functions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str ''dot join''' inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”

seq = ("a", "b", "c")

print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''

Type

'''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''

'''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

'''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''a-b-c'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined '''a, b, c''' with '''hyphen'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str dot split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''

Type as shown press '''Enter'''

'''print str dot split''' ''open and close parentheses'' press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''['Line1-abcdef', 'Line2-abc', 'Line4-abcd']'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the strings at '''spaces'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly and
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the string ’ is called the apostrophe, to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are strings and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the string ’ is called the apostrophe, to variable s
# How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'.
# The variables '''s''' and '''t''' are strings and '''r''' is integer.

They are assigned with the values as shown below,
What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value
# The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2018-01-22T09:56:04Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3''' and
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x ''is equal to''' inside quotes'' '''Hello'''

Press '''Enter'''

'''y ''is equal to''' inside quotes'' '''World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.'''''

Press '''Enter'''

'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''Hello, World!'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

Type '''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight '''HelloHelloHelloHelloHello'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type,

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages'''

Press '''Enter'''

'''print''' ''inside parentheses '' '''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual '''elements''' in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>Type a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

Recall '''a.'''

Press '''Enter'''.

Type,

'''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>Type a[-1] </nowiki>'''

'''<nowiki>Type a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>Type

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''.

Type

'''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''

Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''
Type

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the '''terminal'''.

Recall '''x'''

Press '''Enter'''

Let us manipulate '''x.'''

'''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of '''x[0]''' is '''‘H’'''.

Now we are trying to assign another value '''‘B’''' to '''x[0]'''.

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide '''split()''' and''' join()''' functions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str ''dot join''' inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”

seq = ("a", "b", "c")

print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''

Type

'''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''

'''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

'''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''a-b-c'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined '''a, b, c''' with '''hyphen'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str dot split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''

Type as shown press '''Enter'''

'''print str dot split''' ''open and close parentheses'' press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''['Line1-abcdef', 'Line2-abc', 'Line4-abcd']'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the strings at '''spaces'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly and
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the string ’ is called the apostrophe, to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are strings and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the string ’ is called the apostrophe, to a variable s
# How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'.
# The variables '''s''' and '''t''' are strings and '''r''' is integer.

They are assigned with the values as shown below,
What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value
# The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2018-01-22T09:54:38Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3''' and
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x ''is equal to''' inside quotes'' '''Hello'''

Press '''Enter'''

'''y ''is equal to''' inside quotes'' '''World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.'''''

Press '''Enter'''

'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''Hello, World!'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

Type '''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight '''HelloHelloHelloHelloHello'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type,

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages'''

Press '''Enter'''

'''print''' ''inside parentheses '' '''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual '''elements''' in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>Type a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

Recall '''a.'''

Press '''Enter'''.

Type,

'''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>Type a[-1] </nowiki>'''

'''<nowiki>Type a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>Type

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''.

Type

'''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''

Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''
Type

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the '''terminal'''.

Recall '''x'''

Press '''Enter'''

Let us manipulate '''x.'''

'''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of '''x[0]''' is '''‘H’'''.

Now we are trying to assign another value '''‘B’''' to '''x[0]'''.

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide '''split()''' and''' join()''' functions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str ''dot join''' inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”

seq = ("a", "b", "c")

print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''

Type

'''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''

'''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

'''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''a-b-c'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined '''a, b, c''' with '''hyphen'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str dot split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''

Type as shown press '''Enter'''

'''print str dot split''' ''open and close parentheses'' press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''['Line1-abcdef', 'Line2-abc', 'Line4-abcd']'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the strings at '''spaces'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly and
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the string ’ is called the apostrophe, to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are strings and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the string ’ is called the apostrophe, to a variable s
# How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'.
# The variables '''s''' and '''t''' are strings and '''r''' is integer.

They are assigned with the values as shown above,
What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value
# The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2018-01-22T09:53:50Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3''' and
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x ''is equal to''' inside quotes'' '''Hello'''

Press '''Enter'''

'''y ''is equal to''' inside quotes'' '''World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.'''''

Press '''Enter'''

'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''Hello, World!'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

Type '''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight '''HelloHelloHelloHelloHello'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type,

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages'''

Press '''Enter'''

'''print''' ''inside parentheses '' '''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual '''elements''' in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>Type a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

Recall '''a.'''

Press '''Enter'''.

Type,

'''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>Type a[-1] </nowiki>'''

'''<nowiki>Type a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>Type

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''.

Type

'''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''

Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''
Type

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the '''terminal'''.

Recall '''x'''

Press '''Enter'''

Let us manipulate '''x.'''

'''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of '''x[0]''' is '''‘H’'''.

Now we are trying to assign another value '''‘B’''' to '''x[0]'''.

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide '''split()''' and''' join()''' functions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str ''dot join''' inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”

seq = ("a", "b", "c")

print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''

Type

'''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''

'''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

'''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''a-b-c'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined '''a, b, c''' with '''hyphen'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str dot split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''

Type as shown press '''Enter'''

'''print str dot split''' ''open and close parentheses'' press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''['Line1-abcdef', 'Line2-abc', 'Line4-abcd']'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the strings at '''spaces'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly and
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the string ’ is called the apostrophe, to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are strings and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the given string to variable '''s'''
# How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'.
# The variables '''s''' and '''t''' are strings and '''r''' is integer.

They are assigned with the values as shown above,
What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value
# The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2018-01-22T09:52:59Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3''' and
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x ''is equal to''' inside quotes'' '''Hello'''

Press '''Enter'''

'''y ''is equal to''' inside quotes'' '''World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.'''''

Press '''Enter'''

'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''Hello, World!'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

Type '''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight '''HelloHelloHelloHelloHello'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type,

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages'''

Press '''Enter'''

'''print''' ''inside parentheses '' '''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual '''elements''' in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>Type a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

Recall '''a.'''

Press '''Enter'''.

Type,

'''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>Type a[-1] </nowiki>'''

'''<nowiki>Type a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>Type

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''.

Type

'''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''

Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''
Type

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the '''terminal'''.

Recall '''x'''

Press '''Enter'''

Let us manipulate '''x.'''

'''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of '''x[0]''' is '''‘H’'''.

Now we are trying to assign another value '''‘B’''' to '''x[0]'''.

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide '''split()''' and''' join()''' functions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str ''dot join''' inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”

seq = ("a", "b", "c")

print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''

Type

'''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''

'''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

'''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''a-b-c'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined '''a, b, c''' with '''hyphen'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str dot split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''

Type as shown press '''Enter'''

'''print str dot split''' ''open and close parentheses'' press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''['Line1-abcdef', 'Line2-abc', 'Line4-abcd']'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the strings at '''spaces'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly.
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the string ’ is called the apostrophe, to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are strings and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the given string to variable '''s'''
# How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'.
# The variables '''s''' and '''t''' are strings and '''r''' is integer.

They are assigned with the values as shown above,
What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value
# The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2018-01-22T09:48:28Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3''' and
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x ''is equal to''' inside quotes'' '''Hello'''

Press '''Enter'''

'''y ''is equal to''' inside quotes'' '''World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.'''''

Press '''Enter'''

'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''Hello, World!'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

Type '''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight '''HelloHelloHelloHelloHello'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type,

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages'''

Press '''Enter'''

'''print''' ''inside parentheses '' '''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual '''elements''' in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>Type a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

Recall '''a.'''

Press '''Enter'''.

Type,

'''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>Type a[-1] </nowiki>'''

'''<nowiki>Type a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>Type

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''.

Type

'''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''

Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''
Type

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the '''terminal'''.

Recall '''x'''

Press '''Enter'''

Let us manipulate '''x.'''

'''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of '''x[0]''' is '''‘H’'''.

Now we are trying to assign another value '''‘B’''' to '''x[0]'''.

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide '''split()''' and''' join()''' functions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str ''dot join''' inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”

seq = ("a", "b", "c")

print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''

Type

'''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''

'''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

'''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''a-b-c'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined '''a, b, c''' with '''hyphen'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str dot split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''

Type as shown press '''Enter'''

'''print str dot split''' ''open and close parentheses'' press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''['Line1-abcdef', 'Line2-abc', 'Line4-abcd']'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the string at '''spaces'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly.
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the string ’ is called the apostrophe, to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are strings and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the given string to variable '''s'''
# How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'.
# The variables '''s''' and '''t''' are strings and '''r''' is integer.

They are assigned with the values as shown above,
What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value
# The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

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Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-files/English

2018-01-09T08:42:47Z

Trupti:

'''Title of script''': '''Getting started with files'''

'''Author: Trupti Kini'''

'''Keywords: IPython, files, read, write, append, mode, splitlines()'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''files'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to -

# Open a file.
# Read the contents of the file line by line.
# Read the entire content of the file at once.
# Append the lines of a file to a list and
# Close the file.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3 '''and
* '''IPython 5.1.0''' 

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know about

* Lists and
* '''for''' statement

If not, see the pre-requisite Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

Highlight according to narration: (open and file object)

'''''syntax:'''''

'''''file_object <nowiki>= open(</nowiki>filename, mode)'''''

Filename - name of the file to be opened.

Mode- indicates how the file is going to be opened.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To open a file for reading or writing, we can use a built in function called '''open()'''.

'''Open() '''function returns a file object.

The syntax is shown here:

'''Filename''' - is the name of the file to be opened.

'''Mode'''- This indicates how the file is going to be opened.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

'''''syntax:'''''

'''''file_object <nowiki>= open(filename, mode)</nowiki>'''''

r- Read mode

w- Write mode

a -Appending mode

r+ - Read and Write
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| r- represent the Read mode

w- is for Write mode

a - represents Appending mode and

r+ - for both Read and Write mode

Specifying mode is optional.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open pendulum.txt in text editor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us open a file, '''pendulum.txt''' in a text editor.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the columns in the file
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This file contains 2 data columns, length and time of pendulum.

We will be using this text file for our demonstration.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The file '''pendulum.txt''' is available in the code file link of this tutorial.

Please download it in '''Home''' directory and use it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

Press '''Ctrl+Alt+T '''keys

Type

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

Type

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

Let us clear the terminal.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us open the file, '''pendulum.txt.'''

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Type

'''f''''' is equal to''''' open''''' inside parentheses inside quotes '''''pendulum '''''dot '''''txt'''

Here the mode is not specified'''. '''

By default, it is ‘r’.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''f'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us type '''f''' on the '''terminal''' to see what it is.

The file object f, shows the filename and mode of the file, which is open.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''filename '''and '''mode 'r''''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| ''''r' '''stands for '''read''' only '''mode'''.

As you can see, this '''file''' is '''open''' in '''read''' only '''mode'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn to '''read''' the whole '''file''' into a single '''variable'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''pend = f.read()'''

Highlight pend= '''f.read()'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Type'''

'''pend '''''equal to '''''f '''''dot '''''read'' '''open and close parentheses.''

We use the '''read method''' to '''read''' all the contents of the file into the '''variable''', '''pend'''

Press '''Enter'''

To use read method we use the file object dot read method.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''print(pend)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us see what '''pend '''contains, by typing

'''print '''''inside parentheses '''''pend.'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the data
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can see that '''pend''' has all the '''data''' of the '''file pendulum.txt'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend'''Highlight data with newline characters
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type just '''pend''' to see more explicitly, what it contains.

We can see the newline characters as well in the output.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us learn to split the variable '''pend''' into a list of lines in the file.

We use the method '''splitlines''' to '''split''' a '''file''' of data into '''list''' of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend_list = pend.splitlines()'''

'''pend_list'''

Highlight the data into list of lines
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| For this we need to store this '''list '''in a variable, say '''pend_list'''

Type

'''pend_list '''''equal to''''' pend '''''dot '''''splitlines '''''open and close parentheses''

Press '''Enter'''

Type

'''pend '''''underscore '''''list '''

Press '''Enter'''

We got the data into list of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the data into list of lines
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''pend_list''' does not contain '''newline''' '''characters '''like '''\n'''.

This is because the string '''pend''' is '''split''' on the '''newline''' '''characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us learn to read the file line-by-line.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''f.close()'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| But, before that we will have to close the file, since the file has already been read till the end.

Let us close the '''file''' opened into f.

Type '''f '''''dot '''''close '''''open and close parentheses''

Press Enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''closed file'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It is a good programming practice to '''close''' any '''file''' '''objects''' that we have opened, after their job is done.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us, now move on to '''reading''' '''files''' '''line'''-'''by'''-'''line'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video here, try out the following exercise and then resume the video.

Re-open the file '''pendulum.txt''' with '''f''' as the file object.

Recall, that we have closed the file earlier.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type'''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us switch back to the terminal.

To re-open the file again, type

'''f '''''is equal to '''''open '''''inside parentheses inside quotes '''''pendulum.txt'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''for line in f:'''

'''print(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, to '''read''' the '''file''' line-by-line, we '''iterate''' over the '''file''' '''object''' line-by-line, using the '''for''' '''loop'''.

Let us '''iterate''' over the '''file''' line-wise and '''print''' each of the lines.

Let us clear the terminal.

Type

'''for line in f '''''colon ''press '''Enter'''

''four spaces''''' print''''' inside parentheses '''''line'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here, '''line''' is a '''loop''' '''variable''', and it is not a keyword.

We could have used any other '''variable''' name, but '''line''' seems meaningful enough.

Press Enter twice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Instead of just printing the lines, let us append them to a list, say '''line_list'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''<nowiki>line_list = []</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We first '''initialize''' a '''line_list '''as an '''empty-list'''

Type,

line ''underscore ''list ''is'' ''equal to ''open and close square brackets.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight according to narration.

Type

'''for line in open('pendulum.txt'):'''

'''line_list.append(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type the code as

for line in open ''inside parentheses inside quotes ''pendulum ''dot'' txt colon ''press enter''

''four space'' line'' underscore'' list ''dot ''append i''nside parentheses'' line

Press Enter twice.

Here, the '''for''' loop '''reads''' the file '''pendulum.txt '''line-by-line .

The '''append''' method will add each of the line to the list, '''line_list.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We could, as usual '''close''' the file using '''f.close() '''and re-open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| But, this time, let's leave alone the '''file''' '''object''' '''f '''and directly open the file within the '''for''' '''statement'''.

This will save us the trouble of closing the file, each time we open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''line_list '''and press '''Enter'''

Highlight data
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us see what '''line_list''' contains.

Type '''line '''''underscore '''''list '''and press '''Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''newline characters'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| If you noticed, '''line '''''underscore '''''list''' is a list of the lines in the file, along with the '''newline''' '''characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can '''strip''' out the '''newline''' '''characters''' from the lines by using some string methods.

This will be covered in the further tutorial on strings.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we learnt to -

# Open and close files using the '''open''' and '''close''' methods respectively.
# Read the data in the files as a whole, by using the '''read''' method.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

# Read the data in the files line by line by iterating over the file object using the '''for loop'''.
# Append the lines of a file to a list using the '''append''' method within the '''for loop'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. The '''open''' function returns a

* string
* list
* file object
* function

2. What does the function '''splitlines()''' do.

* Displays the '''data''' as '''strings''', all in a line
* Displays the '''data''' line by line as '''strings'''
* Displays the '''data''' line by line but not as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers are,

# '''open '''function returns a '''file object'''
# '''splitlines() '''displays the '''data''' line by line as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-files/English

2018-01-09T08:41:15Z

Trupti:

'''Title of script''': '''Getting started with files'''

'''Author: Trupti Kini'''

'''Keywords: IPython, files, read, write, append, mode, splitlines()'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''files'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to -

# Open a file.
# Read the contents of the file line by line.
# Read the entire content of the file at once.
# Append the lines of a file to a list and
# Close the file.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3 '''and
* '''IPython 5.1.0''' 

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know about

* Lists and
* '''for''' statement

If not, see the pre-requisite Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

Highlight according to narration: (open and file object)

'''''syntax:'''''

'''''file_object <nowiki>= open(</nowiki>filename, mode)'''''

Filename - name of the file to be opened.

Mode- indicates how the file is going to be opened.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To open a file for reading or writing, we can use a built in function called '''open()'''.

'''Open() '''function returns a file object.

The syntax is shown here:

'''Filename''' - is the name of the file to be opened.

'''Mode'''- This indicates how the file is going to be opened.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

'''''syntax:'''''

'''''file_object <nowiki>= open(filename, mode)</nowiki>'''''

r- Read mode

w- Write mode

a -Appending mode

r+ - Read and Write
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| r- represent the Read mode

w- is for Write mode

a - represents Appending mode and

r+ - for both Read and Write mode

Specifying mode is optional.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open pendulum.txt in text editor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us open a file, '''pendulum.txt''' in a text editor.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the columns in the file
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This file contains 2 data columns, length and time of pendulum.

We will be using this text file for our demonstration.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The file '''pendulum.txt''' is available in the code file link of this tutorial.

Please download it in '''Home''' directory and use it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

Press '''Ctrl+Alt+T '''keys

Type

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

Type

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

Let us clear the terminal.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us open the file, '''pendulum.txt.'''

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Type

'''f''''' is equal to''''' open''''' inside parentheses inside quotes '''''pendulum '''''dot '''''txt'''

Here the mode is not specified'''. '''

By default, it is ‘r’.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''f'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us type '''f''' on the '''terminal''' to see what it is.

The file object f, shows the filename and mode of the file, which is open.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''filename '''and '''mode 'r''''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| ''''r' '''stands for '''read''' only '''mode'''.

As you can see, this '''file''' is '''open''' in '''read''' only '''mode'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn to '''read''' the whole '''file''' into a single '''variable'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''pend = f.read()'''

Highlight pend= '''f.read()'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Type'''

'''pend '''''equal to '''''f '''''dot '''''read'' '''open and close parentheses.''

We use the '''read method''' to '''read''' all the contents of the file into the '''variable''', '''pend'''

Press '''Enter'''

To use read method we use the file object dot read method.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''print(pend)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us see what '''pend '''contains, by typing

'''print '''''inside parentheses '''''pend.'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the data
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can see that '''pend''' has all the '''data''' of the '''file pendulum.txt'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend'''Highlight data with newline characters
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type just '''pend''' to see more explicitly, what it contains.

We can see the newline characters as well in the output.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us learn to split the variable '''pend''' into a list of lines in the file.

We use the method '''splitlines''' to '''split''' a '''file''' of data into '''list''' of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend_list = pend.splitlines()'''

'''pend_list'''

Highlight the data into list of lines
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| For this we need to store this '''list '''in a variable, say '''pend_list'''

Type

'''pend_list '''''equal to''''' pend '''''dot '''''splitlines '''''open and close parentheses''

Press '''Enter'''

Type

'''pend '''''underscore '''''list '''

Press '''Enter'''

We got the data into list of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the data into list of lines
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''pend_list''' does not contain '''newline''' '''characters '''like '''\n'''.

This is because the string '''pend''' is '''split''' on the '''newline''' '''characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us learn to read the file line-by-line.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''f.close()'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| But, before that we will have to close the file, since the file has already been read till the end.

Let us close the '''file''' opened into f.

Type '''f '''''dot '''''close '''''open and close parentheses''

Press Enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''closed file'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It is a good programming practice to '''close''' any '''file''' '''objects''' that we have opened, after their job is done.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us, now move on to '''reading''' '''files''' '''line'''-'''by'''-'''line'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video here, try out the following exercise and then resume the video.

Re-open the file '''pendulum.txt''' with '''f''' as the file object.

Recall, that we have closed the file earlier.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type'''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us switch back to the terminal.

To re-open the file again, type

'''f '''''is equal to '''''open '''''inside parentheses inside quotes '''''pendulum.txt'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''for line in f:'''

'''print(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, to '''read''' the '''file''' line-by-line, we '''iterate''' over the '''file''' '''object''' line-by-line, using the '''for''' '''loop'''.

Let us '''iterate''' over the '''file''' line-wise and '''print''' each of the lines.

Let us clear the terminal.

Type

'''for line in f '''''colon ''press '''Enter'''

''four spaces''''' print''''' inside parentheses '''''line'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here, '''line''' is a '''loop''' '''variable''', and it is not a keyword.

We could have used any other '''variable''' name, but '''line''' seems meaningful enough.

Press Enter twice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Instead of just printing the lines, let us append them to a list, say '''line_list'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''<nowiki>line_list = []</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We first '''initialize''' a '''line_list '''as an '''empty-list'''

Type,

line ''underscore ''list ''is'' ''equal to ''open and close square brackets.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight according to narration.

Type

'''for line in open('pendulum.txt'):'''

'''line_list.append(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type the code as

for line in open ''inside parentheses inside quotes ''pendulum ''dot'' txt colon ''press enter''

''four space'' line'' underscore'' list ''dot ''append i''nside parentheses'' line

Press Enter twice.

Here, the '''for''' loop '''reads''' the file '''pendulum.txt '''line-by-line .

The '''append''' method will add each of the line to the list, '''line_list.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We could, as usual '''close''' the file using '''f.close() '''and re-open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| But, this time, let's leave alone the '''file''' '''object''' '''f '''and directly open the file within the '''for''' '''statement'''.

This will save us the trouble of closing the file, each time we open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''line_list '''and press '''Enter'''

Highlight data
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us see what '''line_list''' contains.

Type '''line '''''underscore '''''list '''and press '''Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''newline characters'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| If you noticed, '''line '''''underscore '''''list''' is a list of the lines in the file, along with the '''newline''' '''characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can '''strip''' out the '''newline''' '''characters''' from the lines by using some string methods.

This will be covered in the further tutorial on strings.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we learnt to -

# Open and close files using the '''open''' and '''close''' methods respectively.
# Read the data in the files as a whole, by using the '''read''' method.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

# Read the data in the files line by line by iterating over the file object using the '''for loop'''.
# Append the lines of a file to a list using the '''append''' method within the '''for loop'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# The '''open''' function returns a

* string
* list
* file object
* function

2. What does the function '''splitlines()''' do.

* Displays the '''data''' as '''strings''', all in a line
* Displays the '''data''' line by line as '''strings'''
* Displays the '''data''' line by line but not as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers are,

# '''open '''function returns a '''file object'''
# '''splitlines() '''displays the '''data''' line by line as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-files/English

2018-01-09T08:11:15Z

Trupti:

'''Title of script''': '''Getting started with files'''

'''Author: Trupti Kini'''

'''Keywords: IPython, files, read, write, append, mode, splitlines()'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''files'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to -

# Open a file.
# Read the contents of the file line by line.
# Read the entire content of the file at once.
# Append the lines of a file to a list and
# Close the file.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3 '''and
* '''IPython 5.1.0''' 

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know about

* Lists and
* '''for''' statement

If not, see the pre-requisite Python tutorials on this website.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

Highlight according to narration: (open and file object)

'''''syntax:'''''

'''''file_object <nowiki>= open(</nowiki>filename, mode)'''''

Filename - name of the file to be opened.

Mode- indicates how the file is going to be opened.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To open a file for reading or writing, we can use a built in function called '''open()'''.

'''Open() '''function returns a file object.

The syntax is shown here:

'''Filename''' - is the name of the file to be opened.

'''Mode'''- This indicates how the file is going to be opened.

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Open a file

'''''syntax:'''''

'''''file_object <nowiki>= open(filename, mode)</nowiki>'''''

r- Read mode

w- Write mode

a -Appending mode

r+ - Read and Write
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| r- represent the Read mode

w- is for Write mode

a - represents Appending mode and

r+ - for both Read and Write mode

Specifying mode is optional.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open pendulum.txt in text editor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us open a file, '''pendulum.txt''' in a text editor.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the columns in the file
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This file contains 2 data columns, length and time of pendulum.

We will be using this text file for our demonstration.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The file '''pendulum.txt''' is available in the code file link of this tutorial.

Please download it in '''Home''' directory and use it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

Press '''Ctrl+Alt+T '''keys

Type

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

Type

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

Let us clear the terminal.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us open the file, '''pendulum.txt.'''

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Type

'''f''''' is equal to''''' open''''' inside parentheses inside quotes '''''pendulum '''''dot '''''txt'''

Here the mode is not specified'''. '''

By default, it is ‘r’.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''f'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us type '''f''' on the '''terminal''' to see what it is.

The file object f, shows the filename and mode of the file, which is open.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''filename '''and '''mode 'r''''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| ''''r' '''stands for '''read''' only '''mode'''.

As you can see, this '''file''' is '''open''' in '''read''' only '''mode'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn to '''read''' the whole '''file''' into a single '''variable'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''pend = f.read()'''

Highlight pend= '''f.read()'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Type'''

'''pend '''''equal to '''''f '''''dot '''''read'' '''open and close parentheses.''

We use the '''read method''' to '''read''' all the contents of the file into the '''variable''', '''pend'''

Press '''Enter'''

To use read method we use the file object dot read method.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''print(pend)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us see what '''pend '''contains, by typing

'''print '''''inside parentheses '''''pend.'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the data
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can see that '''pend''' has all the '''data''' of the '''file pendulum.txt'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend'''Highlight data with newline characters
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type just '''pend''' to see more explicitly, what it contains.

We can see the newline characters as well in the output.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us learn to split the variable '''pend''' into a list of lines in the file.

We use the method '''splitlines''' to '''split''' a '''file''' of data into '''list''' of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend_list = pend.splitlines()'''

'''pend_list'''

Highlight the data into list of lines
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| For this we need to store this '''list '''in a variable, say '''pend_list'''

Type

'''pend_list '''''equal to''''' pend '''''dot '''''splitlines '''''open and close parentheses''

Press '''Enter'''

Type

'''pend '''''underscore '''''list '''

Press '''Enter'''

We got the data into list of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the data into list of lines
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''pend_list''' does not contain '''newline''' '''characters '''like '''\n'''.

This is because the string '''pend''' is '''split''' on the '''newline''' '''characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us learn to read the file line-by-line.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''f.close()'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| But, before that we will have to close the file, since the file has already been read till the end.

Let us close the '''file''' opened into f.

Type '''f '''''dot '''''close '''''open and close parentheses''

Press Enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''closed file'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It is a good programming practice to '''close''' any '''file''' '''objects''' that we have opened, after their job is done.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us, now move on to '''reading''' '''files''' '''line'''-'''by'''-'''line'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video here, try out the following exercise and then resume the video.

Re-open the file '''pendulum.txt''' with '''f''' as the file object.

Recall, that we have closed the file earlier.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type'''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us switch back to the terminal.

To re-open the file again, type

'''f '''''is equal to '''''open '''''inside parentheses inside quotes '''''pendulum.txt'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''for line in f:'''

'''print(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, to '''read''' the '''file''' line-by-line, we '''iterate''' over the '''file''' '''object''' line-by-line, using the '''for''' '''loop'''.

Let us '''iterate''' over the '''file''' line-wise and '''print''' each of the lines.

Let us clear the terminal.

Type

'''for line in f '''''colon ''press '''Enter'''

''four spaces''''' print''''' inside parentheses '''''line'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here, '''line''' is a '''loop''' '''variable''', and it is not a keyword.

We could have used any other '''variable''' name, but '''line''' seems meaningful enough.

Press Enter twice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Instead of just printing the lines, let us append them to a list, say '''line_list'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''<nowiki>line_list = []</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We first '''initialize''' a '''line_list '''as an '''empty-list'''

Type,

line ''underscore ''list ''is'' ''equal to ''open and close square brackets.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight according to narration.

Type

'''for line in open('pendulum.txt'):'''

'''line_list.append(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type the code as

for line in open ''inside parentheses inside quotes ''pendulum ''dot'' txt colon ''press enter''

''four space'' line'' underscore'' list ''dot ''append i''nside parentheses'' line

Press Enter twice.

Here, the '''for''' loop '''reads''' the file '''pendulum.txt '''line-by-line .

The '''append''' method will add each of the line to the list, '''line_list.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We could, as usual '''close''' the file using '''f.close() '''and re-open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| But, this time, let's leave alone the '''file''' '''object''' '''f '''and directly open the file within the '''for''' '''statement'''.

This will save us the trouble of closing the file, each time we open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''line_list '''and press '''Enter'''

Highlight data
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us see what '''line_list''' contains.

Type '''line '''''underscore '''''list '''and press '''Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''newline characters'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| If you noticed, '''line '''''underscore '''''list''' is a list of the lines in the file, along with the '''newline''' '''characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can '''strip''' out the '''newline''' '''characters''' from the lines by using some string methods.

This will be covered in the further tutorial on strings.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we learnt to -

# Open and close files using the '''open''' and '''close''' methods respectively.
# Read the data in the files as a whole, by using the '''read''' method.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| # Read the data in the files line by line by iterating over the file object using the '''for loop'''.
# Append the lines of a file to a list using the '''append''' method within the '''for loop'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# The '''open''' function returns a

* string
* list
* file object
* function

2. What does the function '''splitlines()''' do.

* Displays the '''data''' as '''strings''', all in a line
* Displays the '''data''' line by line as '''strings'''
* Displays the '''data''' line by line but not as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers are,

# '''open '''function returns a '''file object'''
# '''splitlines() '''displays the '''data''' line by line as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-files/English

2018-01-09T08:05:25Z

Trupti:

'''Title of script''': '''Getting started with files'''

'''Author: Trupti Kini'''

'''Keywords: IPython, files, read, write, append, mode, splitlines()'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''files'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to -

# Open a file.
# Read the contents of the file line by line.
# Read the entire content of the file at once.
# Append the lines of a file to a list and
# Close the file.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3 '''and
* '''IPython 5.1.0''' 

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know about

* Lists and
* '''for''' statement

If not, see the pre-requisite Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

Highlight according to narration: (open and file object)

'''''syntax:'''''

'''''file_object <nowiki>= open(</nowiki>filename, mode)'''''

Filename - name of the file to be opened.

Mode- indicates how the file is going to be opened.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To open a file for reading or writing, we can use a built in function called '''open()'''.

'''Open() '''function returns a file object.

The syntax is shown here:

'''Filename''' - is the name of the file to be opened.

'''Mode'''- This indicates how the file is going to be opened.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

'''''syntax:'''''

'''''file_object <nowiki>= open(filename, mode)</nowiki>'''''

r- Read mode

w- Write mode

a -Appending mode

r+ - Read and Write
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| r- represent the Read mode

w- is for Write mode

a - represents Appending mode and

r+ - for both Read and Write mode

Specifying mode is optional.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open pendulum.txt in text editor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us open a file, '''pendulum.txt''' in a text editor.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the columns in the file
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This file contains 2 data columns, length and time of pendulum.

We will be using this text file for our demonstration.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The file '''pendulum.txt''' is available in the code file link of this tutorial.

Please download it in '''Home''' directory and use it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

Press '''Ctrl+Alt+T '''keys

Type

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

Type

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

Let us clear the terminal.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us open the file, '''pendulum.txt.'''

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Type

'''f''''' is equal to''''' open''''' inside parentheses inside quotes '''''pendulum '''''dot '''''txt'''

Here the mode is not specified'''. '''

By default, it is ‘r’.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''f'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us type '''f''' on the '''terminal''' to see what it is.

The file object f, shows the filename and mode of the file, which is open.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''filename '''and '''mode 'r''''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| ''''r' '''stands for '''read''' only '''mode'''.

As you can see, this '''file''' is '''open''' in '''read''' only '''mode'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn to '''read''' the whole '''file''' into a single '''variable'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''pend = f.read()'''

Highlight pend= '''f.read()'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Type'''

'''pend '''''equal to '''''f '''''dot '''''read'' '''open and close parentheses.''

We use the '''read method''' to '''read''' all the contents of the file into the '''variable''', '''pend'''

Press '''Enter'''

To use read method we use the file object dot read method.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''print(pend)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us see what '''pend '''contains, by typing

'''print '''''inside parentheses '''''pend.'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the data
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can see that '''pend''' has all the '''data''' of the '''file pendulum.txt'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend'''Highlight data with newline characters
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type just '''pend''' to see more explicitly, what it contains.

We can see the newline characters as well in the output.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us learn to split the variable '''pend''' into a list of lines in the file.

We use the method '''splitlines''' to '''split''' a '''file''' of data into '''list''' of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend_list = pend.splitlines()'''

'''pend_list'''

Highlight the data into list of lines
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| For this we need to store this '''list '''in a variable, say '''pend_list'''

Type

'''pend_list '''''equal to''''' pend '''''dot '''''splitlines '''''open and close parentheses''

Press '''Enter'''

Type

'''pend '''''underscore '''''list '''

Press '''Enter'''

We got the data into list of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the data into list of lines
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''pend_list''' does not contain '''newline''' '''characters '''like '''\n'''.

This is because the string '''pend''' is '''split''' on the '''newline''' '''characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us learn to read the file line-by-line.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''f.close()'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| But, before that we will have to close the file, since the file has already been read till the end.

Let us close the '''file''' opened into f.

Type '''f '''''dot '''''close '''''open and close parentheses''

Press Enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''closed file'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It is a good programming practice to '''close''' any '''file''' '''objects''' that we have opened, after their job is done.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us, now move on to '''reading''' '''files''' '''line'''-'''by'''-'''line'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video here, try out the following exercise and then resume the video.

Re-open the file '''pendulum.txt''' with '''f''' as the file object.

Recall, that we have closed the file earlier.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type'''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us switch back to the terminal.

To re-open the file again, type

'''f '''''is equal to '''''open '''''inside parentheses inside quotes '''''pendulum.txt'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''for line in f:'''

'''print(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, to '''read''' the '''file''' line-by-line, we '''iterate''' over the '''file''' '''object''' line-by-line, using the '''for''' '''loop'''.

Let us '''iterate''' over the '''file''' line-wise and '''print''' each of the lines.

Let us clear the terminal.

Type

'''for line in f '''''colon ''press '''Enter'''

''four spaces''''' print''''' inside parentheses '''''line'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here, '''line''' is a '''loop''' '''variable''', and it is not a keyword.

We could have used any other '''variable''' name, but '''line''' seems meaningful enough.

Press Enter twice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Instead of just printing the lines, let us append them to a list, say '''line_list'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''<nowiki>line_list = []</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We first '''initialize''' a '''line_list '''as an '''empty-list'''

Type,

line ''underscore ''list ''is'' ''equal to ''open and close square brackets.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight according to narration.

Type

'''for line in open('pendulum.txt'):'''

'''line_list.append(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type the code as

for line in open ''inside parentheses inside quotes ''pendulum ''dot'' txt colon ''press enter''

''four space'' line'' underscore'' list ''dot ''append i''nside parentheses'' line

Press Enter twice.

Here, the '''for''' loop '''reads''' the file '''pendulum.txt '''line-by-line .

The '''append''' method will add each of the line to the list, '''line_list.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We could, as usual '''close''' the file using '''f.close() '''and re-open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| But, this time, let's leave alone the '''file''' '''object''' '''f '''and directly open the file within the '''for''' '''statement'''.

This will save us the trouble of closing the file, each time we open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''line_list '''and press '''Enter'''

Highlight data
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us see what '''line_list''' contains.

Type '''line '''''underscore '''''list '''and press '''Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''newline characters'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| If you noticed, '''line '''''underscore '''''list''' is a list of the lines in the file, along with the '''newline''' '''characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can '''strip''' out the '''newline''' '''characters''' from the lines by using some string methods.

This will be covered in the further tutorial on strings.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we learnt to -

# Open and close files using the '''open''' and '''close''' methods respectively.
# Read the data in the files as a whole, by using the '''read''' method.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| # Read the data in the files line by line by iterating over the file object using the '''for loop'''.
# Append the lines of a file to a list using the '''append''' method within the '''for loop'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# The '''open''' function returns a

* string
* list
* file object
* function

2. What does the function '''splitlines()''' do.

* Displays the '''data''' as '''strings''', all in a line
* Displays the '''data''' line by line as '''strings'''
* Displays the '''data''' line by line but not as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers are,

# '''open '''function returns a '''file object'''
# '''splitlines() '''displays the '''data''' line by line as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-files/English

2018-01-08T14:28:05Z

Trupti:

'''Python/C2/Getting-started-with-files/English''''''Title of script''': Getting started with '''files'''

'''Author: Trupti Kini'''

'''Keywords: Python, IPython, files, '''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''files'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able learn to -

# Open a file.
# Read the contents of the file line by line.
# Read the entire content of the file at once.
# Append the lines of a file to a list.
# Close the file.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know about how to-

* Lists and
* '''for''' statement

If not, see the pre-requisite Python tutorials on http://spoken-tutorial.org

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

Highlight according to narration: (open and fileobject)

'''''syntax:'''''

'''''file_object <nowiki>= open(“filename”, “mode”)</nowiki>'''''

Filename - name of the file to be opened.

Mode- indicates how the file is going to be opened.

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To open a file for reading or writing, we can use a built in function called open().

Open() function returns a file object.

The syntax is shown here:

Filename - is the name of the file to be opened.

Mode- This indicates how the file is going to be opened.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

'''''syntax:'''''

'''''f <nowiki>= open(“filename”, “mode”)</nowiki>'''''

r- Read mode

w- Write mode

a -Appending mode

r+ - Read and Write
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| r- represent the Read mode

w- is for Write mode

a - represents Appending mode and

r+ - for both Read and Write mode

Specifying mode is optional.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open pendulum.txt in text editor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us open a file, '''pendulum.txt''' in a text editor.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the columns in the file
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This file contains 2 data columns, length and time of pendulum.

We will be using this text file for our demonstration.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The file '''pendulum.txt''' is available in the code file link of this tutorial.

Please download it in '''Home''' directory and use it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us open the file, '''pendulum.txt.'''

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Type

'''f''''' is equal to''''' open''''' inside parentheses inside quotes '''''pendulum '''''dot '''''txt'''

Here the mode is not specified'''. '''By default, it is ‘r’.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''f'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us type '''f''' on the '''terminal''' to see what it is.

The file object f, shows the filepath and mode of the file, which is open.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''filepath '''and '''mode 'r''''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| ''''r' '''stands for '''read''' only '''mode'''.

As you can see, this '''file''' is '''open''' in '''read''' only '''mode'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn to '''read''' the whole '''file''' into a single '''variable'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''type'''

'''pend = f.read()'''

Highlight pend= '''f.read()'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Type'''

'''pend '''''equal to '''''f '''''dot '''''read'' '''open and close parentheses.''

We use the '''read method''' to '''read''' all the contents of the file into the '''variable''', '''pend'''

Press '''Enter'''

To use read method we use the file object dot read method.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''print(pend)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us see what '''pend '''contains, by typing

'''print '''''inside parentheses '''''pend.'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can see that '''pend''' has all the '''data''' of the '''file pendulum .txt'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''pend'''Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type just '''pend''' to see more explicitly, what it contains.

We can see the newline characters as well in the output.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us learn to split the variable '''pend''' into a list of lines in the file.

We use the method '''splitlines''' to '''split''' a '''file''' of data into '''list''' of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend_list = pend.splitlines()'''

'''pend_list'''

Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| For this we need to store this '''list '''in a variable, say '''pend_list'''

Type

'''pend_list '''''equal to''''' pend '''''dot '''''splitlines '''''open and close parentheses''

Press '''Enter'''

Type

'''pend '''''underscore '''''list '''

Press '''Enter'''

We got the data into list of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''pend_list''' does not contain '''newline''' '''characters '''like '''\n'''.

This is because the string '''pend''' is '''split''' on the '''newline''' '''characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us learn to read the file line-by-line.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''f.close()'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| But, before that we will have to close the file, since the file has already been read till the end.

Let us close the '''file''' opened into f.

Type '''f '''''dot '''''close '''''open and close parentheses''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''closed file'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It is a good programming practice to '''close''' any '''file''' '''objects''' that we have opened, after their job is done.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us, now move on to '''reading''' '''files''' '''line'''-'''by'''-'''line'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video here, try out the following exercise and resume the video.

Re-open the file '''pendulum.txt''' with '''f''' as the file object.

Recall, that we have closed the file earlier.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To re-open the file again, type

'''f '''''is equal to '''''open '''''inside parentheses inside quotes '''''pendulum.txt'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''for line in f:'''

'''print(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, to '''read''' the '''file''' line-by-line, we '''iterate''' over the '''file''' '''object''' line-by-line, using the '''for''' '''loop'''.

Let us '''iterate''' over the '''file''' line-wise and '''print''' each of the lines.

Type

'''for line in f '''''colon ''press '''Enter'''

''four spaces''''' print''''' inside parentheses '''''line'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here, '''line''' is a '''loop''' '''variable''', and it is not a keyword.

We could have used any other '''variable''' name, but '''line''' seems meaningful enough.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Instead of just printing the lines, let us append them to a list, say '''line_list'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>line_list = []</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We first '''initialize''' an '''line_list '''as an '''empty-list'''

Type,

line ''underscore ''list ''equal to ''open and close square brackets.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight according to narration.

'''for line in open('pendulum.txt'):'''

'''line_list.append(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type the code as

for line in open ''inside parentheses inside quotes ''pendulum ''dot'' txt colon ''press enter''

''four space'' line'' underscore'' list ''dot ''append i''nside parentheses'' line

Here, the '''for''' loop '''reads''' the file '''pendulum.txt '''line-by-line .

The '''append''' method will add each of the line to the list, '''line_list.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We could, as usual '''close''' the file using '''f.close() '''and re-open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| But, this time, let's leave alone the '''file''' '''object''' '''f''' and directly open the file within the '''for''' '''statement'''.

This will save us the trouble of closing the file, each time we open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''line_list '''and press '''Enter'''

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us see what '''line_list''' contains.

Type '''line_list '''and press '''Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''newline character'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| If you noticed, '''line_list''' is a list of the lines in the file, along with the '''newline''' '''characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can '''strip''' out the '''newline''' '''characters''' from the lines by using some string methods.

This will be covered in the further tutorial on strings.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial. In this tutorial, we learnt to -

# Open and close files using the '''open''' and '''close''' methods respectively.
# Read the data in the files as a whole, by using the '''read''' method.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| # Read the data in the files line by line by iterating over the file object using the '''for loop'''.
# Append the lines of a file to a list using the '''append''' '''method''' within the '''for loop'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# The '''open''' function returns a

* string
* list
* file object
* function

2. What does the function '''splitlines()''' do.

* Displays the '''data''' as '''strings''', all in a line
* Displays the '''data''' line by line as '''strings'''
* Displays the '''data''' line by line but not as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers are,

# '''open '''function returns a '''file object'''
# '''splitlines() '''displays the '''data''' line by line as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-files/English

2018-01-08T14:18:42Z

Trupti: Created page with "'''Python/C2/Getting-started-with-files/English''''''Title of script''': Getting started with '''files''' '''Author: Trupti Kini''' '''Keywords: Python, IPython, files, '''..."

'''Python/C2/Getting-started-with-files/English''''''Title of script''': Getting started with '''files'''

'''Author: Trupti Kini'''

'''Keywords: Python, IPython, files, '''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''files'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able learn to -

# Open a file.
# Read the contents of the file line by line.
# Read the entire content of the file at once.
# Append the lines of a file to a list.
# Close the file.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know about how to-

* Lists and
* '''for''' statement

If not, see the pre-requisite Python tutorials on http://spoken-tutorial.org

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

Highlight according to narration: (open and fileobject)

'''''sy'''''doneIf you explain the syntax, then the actual code, it is easy to follow. Get suggestion from the content creator'''''ntax:'''''

'''''file_object <nowiki>= open(“filename”, “mode”)</nowiki>'''''

Filename - name of the file to be opened.

Mode- indicates how the file is going to be opened.

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To open a file for reading or writing, we can use a built in function called open().

Open() function returns a file object.

The syntax is shown here:

Filename - is the name of the file to be opened.

Mode- This indicates how the file is going to be opened.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Open a file

'''''sy'''''doneIf you explain the syntax, then the actual code, it is easy to follow. Get suggestion from the content creator'''''ntax:'''''

'''''f <nowiki>= open(“filename”, “mode”)</nowiki>'''''

r- Read mode

w- Write mode

a -Appending mode

r+ - Read and Writewe are specifying the default mode below. So it is not required here.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| r- represent the Read mode

w- is for Write mode

a - represents Appending mode and

r+ - for both Read and Write mode

Specifying mode is optional.

Default mode is r.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open pendulum.txt in text editor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us open a file, '''pendulum.txt''' in a text editor.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the columns in the file
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This file contains 2 data columns, length and time of pendulum.

We will be using this text file for our demonstration.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The file '''pendulum.txt''' is available in the code file link of this tutorial.

Please download it in '''Home''' directory and use it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us open the file, '''pendulum.txt.'''

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''If so, specify that the default mode is r, read mode''''''f = open('pendulum.txt') - should we specify the mode here or leave it empty. if you don't sepcify, is it 'r' mode by default.''''''yes coz that will come when we just type f and press enter''''''Do we need to specify the mode like r, w, a, r+ in the open command'''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Type

'''f''''' is equal to''''' open''''' inside parentheses inside quotes '''''pendulum '''''dot '''''txt'''

Here the mode is not specified'''. '''By default, it is ‘r’.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''f'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us type '''f''' on the '''terminal''' to see what it is.

The file object f, shows the filepath and mode of the file, which is open.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''filepath '''and '''mode 'r''''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| ''''r' '''stands for '''read''' only '''mode'''.

As you can see, this '''file''' is '''open''' in '''read''' only '''mode'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn to '''read''' the whole '''file''' into a single '''variable'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''type'''

'''pend = f.read()'''

Highlight pend= '''f.read()'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Type'''

'''pend '''''equal to '''''f '''''dot '''''read'' '''open and close parentheses.''

We use the '''read method''' to '''read''' all the contents of the file into the '''variable''', '''pend'''

Press '''Enter'''

To use read method we use the file object dot read method.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''print(pend)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us see what '''pend '''contains, by typing

'''print '''''inside parentheses '''''pend.'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Point to the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can see that '''pend''' has all the '''data''' of the '''file pendulum .txt'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''pend'''Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type just '''pend''' to see more explicitly, what it contains.

We can see the newline characters as well in the output.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| doneIt would be better if you teach the method splitlines and then give an example. After that give some exercise for the user to solve. Please check the entire script for the same.<nowiki>[IPython Terminal]</nowiki>doneIt would be better if you teach the method splitlines and then give an example. After that give some exercise for the user to solve. Please check the entire script for the same.

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us learn to split the variable '''pend''' into a list of lines in the file.

We use the method '''splitlines''' to '''split''' a '''file''' of data into '''list''' of lines.doneIt would be better if you teach the method splitlines and then give an example. After that give some exercise for the user to solve. Please check the entire script for the same.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type

'''pend_list = pend.splitlines()'''

'''pend_list'''

Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| doneIt would be better if you teach the method splitlines and then give an example. After that give some exercise for the user to solve. Please check the entire script for the same.For this we need to store this '''list '''in a variable, say '''pend_list'''

Type

'''pend_list '''''equal to''''' pend '''''dot '''''splitlines '''''open and close parentheses''

Press '''Enter'''

Type

'''pend '''''underscore '''''list '''

Press '''Enter'''

We got the data into list of lines.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''pend_list''' does not contain '''newline''' '''characters '''like '''\n'''.

This is because the string '''pend''' is '''split''' on the '''newline''' '''characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us learn to read the file line-by-line.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''f.close()'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| But, before that we will have to close the file, since the file has already been read till the end.

Let us close the '''file''' opened into f.

Type '''f '''''dot '''''close '''''open and close parentheses''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''closed file'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It is a good programming practice to '''close''' any '''file''' '''objects''' that we have opened, after their job is done.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us, now move on to '''reading''' '''files''' '''line'''-'''by'''-'''line'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video here, try out the following exercise and resume the video.

Re-open the file '''pendulum.txt''' with '''f''' as the file object.

Recall, that we have closed the file earlier.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''f = open('pendulum.txt')'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To re-open the file again, type

'''f '''''is equal to '''''open '''''inside parentheses inside quotes '''''pendulum.txt'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''for line in f:'''

'''print(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, to '''read''' the '''file''' line-by-line, we '''iterate''' over the '''file''' '''object''' line-by-line, using the '''for''' '''loop'''.

Let us '''iterate''' over the '''file''' line-wise and '''print''' each of the lines.

Type

'''for line in f '''''colon ''press '''Enter'''

''four spaces''''' print''''' inside parentheses '''''line'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here, '''line''' is a '''loop''' '''variable''', and it is not a keyword.

We could have used any other '''variable''' name, but '''line''' seems meaningful enough.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''line'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Instead of just printing the lines, let us append them to a list, say '''line_list'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>line_list = []</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We first '''initialize''' an '''line_list '''as an '''empty-list'''

Type,

line ''underscore ''list ''equal to ''open and close square brackets.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight according to narration.

'''for line in open('pendulum.txt'):'''

'''line_list.append(line)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type the code as

for line in open ''inside parentheses inside quotes ''pendulum ''dot'' txt colon ''press enter''

''four space'' line'' underscore'' list ''dot ''append i''nside parentheses'' line

Here, the '''for''' loop '''reads''' the file '''pendulum.txt '''line-by-line .

The '''append''' method will add each of the line to the list, '''line_list.'''

Let us then '''read''' the '''file''' line-by-line and then '''append''' each of the lines to the '''line_list'''.

for line in open ''inside parentheses inside quotes ''pendulum ''dot'' txt colon ''press enter''

''four space'' line'' underscore'' list ''dot ''append i''nside parentheses'' line

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We could, as usual '''close''' the file using '''f.close() '''and re-open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| But, this time, let's leave alone the '''file''' '''object''' '''f''' and directly open the file within the '''for''' '''statement'''.

This will save us the trouble of closing the file, each time we open it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Type '''line_list '''and press '''Enter'''

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us see what '''line_list''' contains.

Type '''line_list '''and press '''Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight '''newline character'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| If you noticed, '''line_list''' is a list of the lines in the file, along with the '''newline''' '''characters'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can '''strip''' out the '''newline''' '''characters''' from the lines by using some string methods.

This will be covered in the further tutorial on strings.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial. In this tutorial, we learnt to -

# Open and close files using the '''open''' and '''close''' methods respectively.
# Read the data in the files as a whole, by using the '''read''' method.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| # Read the data in the files line by line by iterating over the file object using the '''for loop'''.
# Append the lines of a file to a list using the '''append''' '''method''' within the '''for loop'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# The '''open''' function returns a

* string
* list
* file object
* function

2. What does the function '''splitlines()''' do.

* Displays the '''data''' as '''strings''', all in a line
* Displays the '''data''' line by line as '''strings'''
* Displays the '''data''' line by line but not as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers are,

# '''open '''function returns a '''file object'''
# '''splitlines() '''displays the '''data''' line by line as '''strings'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-for/English

2018-01-08T14:10:41Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for loop'''.
# Use '''range() function'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use '''lists'''.

If not, see the relevant '''Python''' tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for loop'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
'''for statement''' iterates over the members of a sequence in order, executing the '''block''' each time.

Here the '''loop variable''' takes the value of the '''item''' inside the sequence on each iteration.

For each '''item,''' the '''loop body''' is executed.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''for loop''' and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab package'''.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for loop'''. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the loop variable iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36.

Note that here we used two variables,

* '''numbers -''' which is a '''list''' of numbers
* '''num''' - which is the element of '''list''' under consideration, in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line '''print(“sqrt of”, num, “is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for statement''' indicates the starting of '''loop body'''.

Every '''statement '''in '''loop''' starts with 4 spaces.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line '''print(“sqrt of”, num, “is”, num**0.5)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single '''statement''' in the '''block'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for loop'''.

And the lines after that don't fall in the scope of the '''for loop'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each '''block''' is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home directory'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal. Clear the terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your '''terminal'''.

Let us clear the '''terminal'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as-

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the output

%run -i sqrt_num_list.py

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the square root of the given numbers executed by the '''for loop'''.

This is the '''print statement''' output executed after the '''for loop'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in '''sqrt_num_list.py'''

* Type each line of the code in the '''IPython interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>
Type

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:

'''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Type,

'''numbers ''equal to inside square brackets'' 4, 9, 16, 25, 36''' and press '''Enter'''

'''for num in numbers '''''colon'' Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the '''prompt''' changes to three dots.

And the cursor is not after the three dots but, there are four spaces from the three dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the '''block'''.

The three dots tell you that you are inside a '''block'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki> Type

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop'''.

'''print ''inside parentheses inside quotes sqrt of comma ''num ''comma inside quotes is comma'' num ''asterick asterick which is raised to power of'' 0.5''' and press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the '''statements''' in the '''block'''.

But still the '''interpreter''' is showing three dots.

This means that you are still inside the '''block'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the '''block''', press '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the output

%run -i sqrt_num_list.py

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the '''list''', which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range built-in function''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range start ''comma'' stop ''comma'' step'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

For example:

'''range ''inside parentheses'' one ''comma'' twenty ''comma'' two '''– generates integers from 1 to 19 with step of 2

'''range ''inside parentheses'' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the '''list'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten.

Execute this in the '''Python interpreter'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open a new terminal.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for loop''' in a '''Python terminal''' window.

Open a new '''terminal''' by pressing '''Ctrl+Alt+T''' keys simultaneously.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

Type

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
Start the '''Python interpreter''' by issuing the '''command python '''in the new '''terminal''' and press '''Enter'''.

Type,

'''for i '''in range '''''inside parentheses'' one ''comma ''eleven ''colon'' and '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the '''block'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
Type

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python interpreter''' does not indent the code automatically.

So enter four '''spaces''' and then type the following.

'''print ''inside parentheses'' i ''comma inside quotes ''cube is ''comma'' i ''raised to power of'' three''' press '''Enter'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit '''Enter''', we still see the three dots.

To get out of the '''block''', press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! So the main thing we learnt here is -

* how to use the '''Python interpreter''' and

* the '''IPython interpreter''' to specify '''blocks'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython interpreter''' for ease of use.

The problem can be solved by just using the '''range() function'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type

for i in range(1, 50, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

Let us clear the '''terminal'''.

for''' i ''in range inside parentheses'' one ''comma'' fifty ''comma'' two ''colon '''

press '''Enter '''

'''print'' inside parentheses'' i''' press '''Enter '''twice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight 1 and 50 in '''range '''function
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter i.e. 2
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate '''element'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create '''blocks''' in '''python''' using''' for'''
# Indent the '''blocks''' of code
# Iterate over a list using '''for loop'''
# Use the '''range() function'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for loop''' to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2. '''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 i.e. [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-for/English

2018-01-08T13:56:43Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for loop'''.
# Use '''range() function'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use '''lists'''.

If not, see the relevant '''Python''' tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for loop'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
'''for statement''' iterates over the members of a sequence in order, executing the '''block''' each time.

Here the '''loop variable''' takes the value of the '''item''' inside the sequence on each iteration.

For each '''item,''' the '''loop body''' is executed.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''for loop''' and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab package'''.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for loop'''. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the loop variable iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36.

Note that here we used two variables,

* '''numbers -''' which is a '''list''' of numbers
* '''num''' - which is the element of '''list''' under consideration, in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line '''print(“sqrt of”, num, “is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for statement''' indicates the starting of '''loop body'''.

Every '''statement '''in '''loop''' starts with 4 spaces.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line '''print(“sqrt of”, num, “is”, num**0.5)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single '''statement''' in the '''block'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for loop'''.

And the lines after that don't fall in the scope of the '''for loop'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each '''block''' is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home directory'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal. Clear the terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your '''terminal'''.

Let us clear the '''terminal'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as-

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the output

%run -i sqrt_num_list.py

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the square root of the given numbers executed by the '''for loop'''.

This is the '''print statement''' output executed after the '''for loop'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in '''sqrt_num_list.py'''

* Type each line of the code in the '''IPython interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>Type

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Type,

'''numbers ''equal to inside square brackets'' 4, 9, 16, 25, 36''' and press '''Enter'''

'''for num in numbers '''''colon'' Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the '''prompt''' changes to three dots.

And the cursor is not after the three dots but, there are four spaces from the three dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the '''block'''.

The three dots tell you that you are inside a '''block'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki> Type

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop'''.

'''print ''inside parentheses inside quotes sqrt of comma ''num ''comma inside quotes is comma'' num ''asterick asterick which is raised to power of'' 0.5''' and press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the '''statements''' in the '''block'''.

But still the '''interpreter''' is showing three dots.

This means that you are still inside the '''block'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the '''block''', press '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the output

%run -i sqrt_num_list.py

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the '''list''', which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range built-in function''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range start ''comma'' stop ''comma'' step'''

For example:

'''range ''inside parentheses'' one ''comma'' twenty ''comma'' two '''– generates integers from 1 to 19 with step of 2

'''range ''inside parentheses'' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the '''list'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten.

Execute this in the '''Python interpreter'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open a new terminal.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for loop''' in a '''Python terminal''' window.

Open a new '''terminal''' by pressing '''Ctrl+Alt+T''' keys simultaneously.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
Start the '''Python interpreter''' by issuing the '''command python '''in the new '''terminal''' and press '''Enter'''.

Type,

'''for i '''in range '''''inside parentheses'' one ''comma ''eleven ''colon'' and '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the '''block'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python interpreter''' does not indent the code automatically.

So enter four '''spaces''' and then type the following.

'''print ''inside parentheses'' i ''comma inside quotes ''cube is ''comma'' i ''raised to power of'' three''' press '''Enter'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit '''Enter''', we still see the three dots.

To get out of the '''block''', press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! So the main thing we learnt here is -

* how to use the '''Python interpreter''' and

* the '''IPython interpreter''' to specify '''blocks'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython interpreter''' for ease of use.

The problem can be solved by just using the '''range() function'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type

for i in range(1, 50, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

Let us clear the '''terminal'''.

for''' i ''in range inside parentheses'' one ''comma'' fifty ''comma'' two ''colon '''

press '''Enter '''

'''print'' inside parentheses'' i''' press '''Enter '''twice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight 1 and 50 in '''range '''function
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter i.e. 2
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate '''element'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create '''blocks''' in '''python''' using''' for'''
# Indent the '''blocks''' of code
# Iterate over a list using '''for loop'''
# Use the '''range() function'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for loop''' to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2. '''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 i.e. [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2018-01-08T13:09:45Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

'''Keywords: Python, Ipython'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3''' and
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x ''is equal to''' inside quotes'' '''Hello'''

Press '''Enter'''

'''y ''is equal to''' inside quotes'' '''World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.'''''

Press '''Enter'''

'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''Hello, World!'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

Type '''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight '''HelloHelloHelloHelloHello'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type,

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages'''

Press '''Enter'''

'''print''' ''inside parentheses '' '''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual '''elements''' in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>Type a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

Recall '''a.'''

Press '''Enter'''.

Type,

'''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>Type a[-1] </nowiki>'''

'''<nowiki>Type a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>Type

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''.

Type

'''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''

Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>Type s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''
Type

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the '''terminal'''.

Recall '''x'''

Press '''Enter'''

Let us manipulate '''x.'''

'''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of '''x[0]''' is '''‘H’'''.

Now we are trying to assign another value '''‘B’''' to '''x[0]'''.

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide '''split()''' and''' join()''' functions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str ''dot join''' inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”

seq = ("a", "b", "c")

print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''

Type

'''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''

'''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

'''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''a-b-c'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined '''a, b, c''' with '''hyphen'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str dot split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''

Type as shown press '''Enter'''

'''print str dot split''' ''open and close parentheses'' press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''['Line1-abcdef', 'Line2-abc', 'Line4-abcd']'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the string at '''spaces'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly.
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the string ’ is called the apostrophe, to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are strings and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the given string to variable '''s'''
# How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'.
# The variables '''s''' and '''t''' are strings and '''r''' is integer.

They are assigned with the values as shown above,
What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value
# The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2018-01-08T10:34:17Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

'''Keywords: Python, Ipython'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3''' and
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x ''is equal to''' inside quotes'' '''Hello'''

Press '''Enter'''

'''y ''is equal to''' inside quotes'' '''World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.'''''

Press '''Enter'''

'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''Hello, World!'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

Type '''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight '''HelloHelloHelloHelloHello'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type,

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages'''

Press '''Enter'''

'''print''' ''inside parentheses '' '''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual '''elements''' in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>Type a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

Recall '''a.'''

Press '''Enter'''.

Type,

'''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>Type a[-1] </nowiki>'''

'''<nowiki>Type a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>Type

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''.

Type

'''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''

Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the '''terminal'''.

Recall '''x'''

Press '''Enter'''

Let us manipulate '''x.'''

'''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of '''x[0]''' is '''‘H’'''.

Now we are trying to assign another value '''‘B’''' to '''x[0]'''.

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str ''dot join''' inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”
seq = ("a", "b", "c")
print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''

Type

'''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''

'''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

'''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined '''a, b, c''' with '''hyphen'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str dot split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''

Type as shown press '''Enter'''

'''print str dot split''' ''open and close parentheses'' press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the string at '''spaces'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly.
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the string ’ is called the apostrophe, to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are string and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the given string to variable '''s'''
# How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'.
# The variables '''s''' and '''t''' are strings and '''r''' is integer.

They are assigned with the values as shown here,
What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value
# The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2018-01-08T10:25:41Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

'''Keywords: Python, Ipython'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3''' and
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x ''is equal to''' inside quotes'' '''Hello'''

Press '''Enter'''

'''y ''is equal to''' inside quotes'' '''World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.'''''

Press '''Enter'''

'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''Hello, World!'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

Type '''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight '''HelloHelloHelloHelloHello'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type,

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages'''

Press '''Enter'''

'''print''' ''inside parentheses '' '''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual '''elements''' in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

Recall '''a.'''

Press '''Enter'''.

Type,

'''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>a[-1] </nowiki>'''

'''<nowiki>a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''.

Type

'''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''

Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the '''terminal'''.

Recall '''x'''

Press '''Enter'''

Let us manipulate '''x.'''

'''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of '''x[0]''' is '''‘H’'''.

Now we are trying to assign another value '''‘B’''' to '''x[0]'''.

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str ''dot join''' inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”
seq = ("a", "b", "c")
print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''

Type

'''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''

'''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

'''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined '''a, b, c''' with '''hyphen'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str dot split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''

Type as shown press '''Enter'''

'''print str dot split''' ''open and close parentheses'' press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the string at '''spaces'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly.
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the string ’ is called the apostrophe, to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are string and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the given string to variable '''s'''
# How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'.
# The variables '''s''' and '''t''' are strings and '''r''' is integer.

They are assigned with the values as shown here,
What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value
# The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2018-01-08T10:11:33Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

'''Keywords: Python, Ipython'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3''' and
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

Example:

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x ''is equal to''' inside quotes'' '''Hello'''

Press '''Enter'''

'''y ''is equal to''' inside quotes'' '''World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.'''''

Press '''Enter'''

'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''Hello, World!'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

# Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages'''

Press '''Enter'''

'''print''' ''inside parentheses '' '''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual '''elements''' in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

Recall '''a.'''

Press '''Enter'''.

Type,

'''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>a[-1] </nowiki>'''

'''<nowiki>a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''.

Type

'''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''

Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the '''terminal'''.

Recall '''x'''

Press '''Enter'''

Let us manipulate '''x.'''

'''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of '''x[0]''' is '''‘H’'''.

Now we are trying to assign another value '''‘B’''' to '''x[0]'''.

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str ''dot join''' inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”
seq = ("a", "b", "c")
print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''

Type

'''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''

'''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

'''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined '''a, b, c''' with '''hyphen'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str dot split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''

Type as shown press '''Enter'''

'''print str dot split''' ''open and close parentheses'' press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the string at '''spaces'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly.
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the string ’ is called the apostrophe, to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are string and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the given string to variable '''s'''
# How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'.
# The variables '''s''' and '''t''' are strings and '''r''' is integer.

They are assigned with the values as shown here,
What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value
# The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2017-12-29T11:47:12Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

'''Keywords: Python, Ipython'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

Example:

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x ''is equal to''' inside quotes'' '''Hello'''

Press '''Enter'''

'''y ''is equal to''' inside quotes'' '''World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.'''''

Press '''Enter'''

'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

# Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages'''

Press '''Enter'''

'''print''' ''inside parentheses '' '''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual '''elements''' in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

Recall '''a.'''

Press '''Enter'''.

Type,

'''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>a[-1] </nowiki>'''

'''<nowiki>a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''.

Type

'''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''

Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the '''terminal'''.

Recall '''x'''

Press '''Enter'''

Let us manipulate '''x.'''

'''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of '''x[0]''' is '''‘H’'''.

Now we are trying to assign another value '''‘B’''' to '''x[0]'''.

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str ''dot join''' inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”
seq = ("a", "b", "c")
print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''

Type

'''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''

'''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

'''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined '''a, b, c''' with '''hyphen'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str dot split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''

Type as shown press '''Enter'''

'''print str dot split''' ''open and close parentheses'' press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the string at '''spaces'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly.
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the string ’ is called the apostrophe, to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are string and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the given string to variable '''s'''
# How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'.
# The variables '''s''' and '''t''' are strings and '''r''' is integer.

They are assigned with the values as shown here,
What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value
# The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2017-12-29T11:06:05Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

'''Keywords: Python, Ipython'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

Example:

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x ''is equal to''' inside quotes'' '''Hello'''

Press '''Enter'''

'''y ''is equal to''' inside quotes'' '''World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.'''''

Press '''Enter'''

'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

# Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages'''

Press '''Enter'''

'''print''' ''inside parentheses '' '''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual '''elements''' in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

Recall '''a.'''

Press '''Enter'''.

Type,

'''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>a[-1] </nowiki>'''

'''<nowiki>a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''.

Type

'''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''

Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the '''terminal'''.

Recall '''x'''

Press '''Enter'''

Let us manipulate '''x.'''

'''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of '''x[0]''' is '''‘H’'''.

Now we are trying to assign another value '''‘B’''' to '''x[0]'''.

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str ''dot join''' inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”seq = ("a", "b", "c"); print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''

Type

'''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''

'''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

'''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined '''a, b, c''' with '''hyphen'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str dot split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''

Type as shown press '''Enter'''

'''print str dot split''' ''open and close parentheses'' press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the string at '''spaces'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly.
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the given string to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are string and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the given string to variable '''s'''
# How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'.
# The variables '''s''' and '''t''' are strings and '''r''' is integer.

They are assigned with the values as shown below:

'''s=”Hello”'''

'''t=”World”'''

'''r=2'''

What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value
# The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2017-12-29T10:10:20Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

'''Keywords: Python, Ipython'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

Example:

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x ''is equal to''' inside quotes'' '''Hello'''

Press '''Enter'''

'''y ''is equal to''' inside quotes'' '''World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.'''''

Press '''Enter'''

'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

# Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages'''

Press '''Enter'''

'''print''' ''inside parentheses '' '''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual '''elements''' in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

Recall '''a.'''

Press '''Enter'''.

Type,

'''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>a[-1] </nowiki>'''

'''<nowiki>a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''.

Type

'''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''

Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the '''terminal'''.

Recall '''x'''

Press '''Enter'''

Let us manipulate '''x.'''

'''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of '''x[0]''' is '''‘H’'''.

Now we are trying to assign another value '''‘B’''' to '''x[0]'''.

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str ''dot join''' inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”seq = ("a", "b", "c"); print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''

Type

'''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''

'''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

'''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined '''a, b, c''' with '''hyphen'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str dot split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''

Type as shown press '''Enter'''

'''print str dot split''' ''open and close parentheses'' press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the string at '''spaces'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly.
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the given string to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are string and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the string ''inside quotes ''is called the '''apostrophe''' , to variable '''s'''
# How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'.
# The variables '''s''' and '''t''' are strings and '''r''' is integer.

They are assigned with the values as shown below:

'''s=”Hello”'''

'''t=”World”'''

'''r=2'''

What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value.

# The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2017-12-29T10:09:38Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

'''Keywords: Python, Ipython'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

Example:

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x ''is equal to''' inside quotes'' '''Hello'''

Press '''Enter'''

'''y ''is equal to''' inside quotes'' '''World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.'''''

Press '''Enter'''

'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

# Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages'''

Press '''Enter'''

'''print''' ''inside parentheses '' '''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual '''elements''' in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

Recall '''a.'''

Press '''Enter'''.

Type,

'''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>a[-1] </nowiki>'''

'''<nowiki>a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''.

Type

'''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''

Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the '''terminal'''.

Recall '''x'''

Press '''Enter'''

Let us manipulate '''x.'''

'''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of '''x[0]''' is '''‘H’'''.

Now we are trying to assign another value '''‘B’''' to '''x[0]'''.

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str ''dot join''' inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”seq = ("a", "b", "c"); print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''

Type

'''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''

'''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

'''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined '''a, b, c''' with '''hyphen'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str dot split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''

'''''type as shown press '''Enter'''

'''print str dot split''' ''open and close parentheses'' press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the string at '''spaces'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly.
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the given string to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are string and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the string ''inside quotes ''is called the '''apostrophe''' , to variable '''s'''
# How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'.
# The variables '''s''' and '''t''' are strings and '''r''' is integer.

They are assigned with the values as shown below:

'''s=”Hello”'''

'''t=”World”'''

'''r=2'''

What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value.

# The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2017-12-29T10:02:01Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

'''Keywords: Python, Ipython'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

Example:

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x ''is equal to''' inside quotes'' '''Hello'''

Press '''Enter'''

'''y ''is equal to''' inside quotes'' '''World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.'''''

Press '''Enter'''

'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

# Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages'''

Press '''Enter'''

'''print''' ''inside parentheses '' '''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual '''elements''' in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''.

Recall '''a.'''

Press '''Enter'''.

Type,

'''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>a[-1] </nowiki>'''

'''<nowiki>a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''.

Type

'''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''

Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the '''terminal'''.

Recall '''x'''

Press '''Enter'''

Let us manipulate '''x.'''

'''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of '''x[0]''' is '''‘H’'''.

Now we are trying to assign another value '''‘B’''' to '''x[0]'''.

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str ''dot join''' inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”seq = ("a", "b", "c"); print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''.

Let us clear the '''terminal'''

Type

'''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''

'''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

'''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined '''a, b, c''' with '''hyphen'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str dot split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''

'''str ''is equal to '''''type as shown press '''Enter'''

'''print str dot split''' ''open and close parentheses'' press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the string at '''spaces'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly.
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the given string to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are string and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the string ''inside quotes ''is called the '''apostrophe''' , to variable '''s'''
# How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'.
# The variables '''s''' and '''t''' are strings and '''r''' is integer.

They are assigned with the values as shown below:

'''s=”Hello”'''

'''t=”World”'''

'''r=2'''

What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value.

# The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2017-12-12T06:48:22Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

'''Keywords: Python, Ipython'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

Example:

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x '''''is equal to inside quotes''''' Hello'''

Press '''Enter'''

'''y '''''is equal to inside quotes''''' World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z '''''is equal to '''''x '''''plus'' ''inside quotes''''' '''''comma''''' '''''plus''''' y '''''plus''''' '''''inside quotes '''''exclamation mark.'''

Press '''Enter'''

print ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string''' '''variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal

What if we multiply a string with an integer?

Let us find out!

Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

# Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s '''''is equal to inside quotes''''' two percentages '''''plus inside quotes''''' hyphen '''''multiplied by''''' twenty''''' plus''''' '''''inside quotes''''' two percentages'''

Press '''Enter'''

'''print '''''inside parentheses '''''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual elements in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

Recall '''a.'''

Press Enter.

Type,

'''a '''''inside square brackets zero ''press enter, gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative''' '''indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>a[-1] </nowiki>'''

'''<nowiki>a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Let us clear the terminal.

Type

'''s '''''is equal to inside quotes''''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''''minus five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the terminal.

Recall '''x'''

Press Enter

Let us manipulate '''x.'''

'''x '''''inside square brackets '''''zero '''''equal to inside quotes '''''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of <nowiki>x[0] is ‘H’. </nowiki>

<nowiki>Now we are trying to assign another value ‘B’ to x[0].</nowiki>

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str '''''dot join inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”seq = ("a", "b", "c"); print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Let us clear the terminal

Type

s ''is equal to inside quotes '''''hyphen '''press '''Enter'''seq ''is equal to inside parentheses '''''a '''''comma '''''b '''''comma '''''c '''press '''Enter'''

print s ''dot '''''join''''' inside parentheses'' '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined a, b, c with hyphen.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str''' ''dot '''''split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal

str ''is equal to ''type as shown press '''Enter'''print '''str''' ''dot '''''split''' ''open and close parentheses''''' '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the string at spaces.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly.
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the string ' is called the apostrophe , to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are string and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the string ''inside quotes ''is called the apostrophe , to variable s
# How will you change s ''is equal to '''hello' to s ''is equal to capital h '''Hello'.
# The variables s and t are strings and r is integer.

They are assigned with the values as shown below:

s=”Hello”

t=”World”

r=2

What is the output of s ''multiplied by'' r'' plus'' t ''multiplied by'' r?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,''' '''

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value.

# The operation s ''multiplied by'' r'' plus'' t ''multiplied by'' r will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2017-12-12T06:47:44Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

'''Keywords: Python, Ipython'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

Example:

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x '''''is equal to inside quotes''''' Hello'''

Press '''Enter'''

'''y '''''is equal to inside quotes''''' World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z '''''is equal to '''''x '''''plus'' ''inside quotes''''' '''''comma''''' '''''plus''''' y '''''plus''''' '''''inside quotes '''''exclamation mark.'''

Press '''Enter'''

print ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string''' '''variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal

What if we multiply a string with an integer?

Let us find out!

Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

# Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s '''''is equal to inside quotes''''' two percentages '''''plus inside quotes''''' hyphen '''''multiplied by''''' twenty''''' plus''''' '''''inside quotes''''' two percentages'''

Press '''Enter'''

'''print '''''inside parentheses '''''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual elements in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

Recall '''a.'''

Press Enter.

Type,

'''a '''''inside square brackets zero ''press enter, gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative''' '''indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>a[-1] </nowiki>'''

'''<nowiki>a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Let us clear the terminal.

Type

'''s '''''is equal to inside quotes''''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''''minus five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the terminal.

Recall '''x'''

Press Enter

Let us manipulate '''x.'''

'''x '''''inside square brackets '''''zero '''''equal to inside quotes '''''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of <nowiki>x[0] is ‘H’. </nowiki>

<nowiki>Now we are trying to assign another value ‘B’ to x[0].</nowiki>

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str '''''dot join inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”seq = ("a", "b", "c"); print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Let us clear the terminal

Type

s ''is equal to inside quotes '''''hyphen '''press '''Enter'''seq ''is equal to inside parentheses '''''a '''''comma '''''b '''''comma '''''c '''press '''Enter'''

print s ''dot '''''join''''' inside parentheses'' '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined a, b, c with hyphen.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str''' ''dot '''''split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal

str ''is equal to ''type as shown press '''Enter'''print '''str''' ''dot '''''split''' ''open and close parentheses''''' '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the string at spaces.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly.
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the string ' is called the apostrophe , to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are string and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the string ''inside quotes ''is called the apostrophe , to variable s
# How will you change s ''is equal to '''hello' to s ''is equal to capital h '''Hello'.
# The variables s and t are strings and r is integer.

They are assigned with the values as shown below:

s=”Hello”

t=”World”

r=2

What is the output of s ''multiplied by'' r'' plus'' t ''multiplied by'' r?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,''' '''

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value.

# The operation s ''multiplied by'' r'' plus'' t ''multiplied by'' r will print each of the two words twice as

'''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2017-12-12T06:43:03Z

Trupti:

'''Python/C2/Getting Started with Strings/English''''''Title of script''': '''Getting Started with Strings'''

'''Author: Trupti Kini'''

'''Keywords: Python, Ipython'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

containing title, name of the production team along with the logo of MHRD
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will learn to,

# Define strings in different ways.
# Concatenate strings.
# Print a string repeatedly.
# Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Pre-requisites
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to

* run basic '''Python '''commands on the '''ipython console'''

If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

Example:

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| What are '''strings'''?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example:

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

What are Strings?
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is a collection of characters which cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''a = 'Hello, World!' '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

We can assign a '''string''' to a '''variable '''called '''a.'''

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now let us learn string concatenation.

Let us assign strings to variables.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''x = 'Hello' '''

'''y = 'World''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type

'''x '''''is equal to inside quotes''''' Hello'''

Press '''Enter'''

'''y '''''is equal to inside quotes''''' World'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''z = x + ', ' + y + '!''''

'''print(z)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings.

'''z '''''is equal to '''''x '''''plus'' ''inside quotes''''' '''''comma''''' '''''plus''''' y '''''plus''''' '''''inside quotes '''''exclamation mark.'''

Press '''Enter'''

print ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string''' '''variables'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight +
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x * 5'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal

What if we multiply a string with an integer?

Let us find out!

Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal

Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

# Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal for solution.

Type,

'''s '''''is equal to inside quotes''''' two percentages '''''plus inside quotes''''' hyphen '''''multiplied by''''' twenty''''' plus''''' '''''inside quotes''''' two percentages'''

Press '''Enter'''

'''print '''''inside parentheses '''''s'''

Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.

We can access individual elements in the '''string''' using the '''subscripts.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Press Up arrow till we get '''a'''

'''<nowiki>a[0] </nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal.

Recall '''a.'''

Press Enter.

Type,

'''a '''''inside square brackets zero ''press enter, gives us the first '''character''' of the '''string'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''.

We can '''access''' the '''strings''' from the end using '''negative''' '''indices.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

'''<nowiki>a[-1] </nowiki>'''

'''<nowiki>a[-2]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

'''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of the following

'''<nowiki>s[-5]</nowiki>'''

'''<nowiki>s[-10]</nowiki>'''

'''<nowiki>s[-15] </nowiki>'''

'''<nowiki>s[15]</nowiki>'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''s = "Hello World”'''

'''<nowiki>s[-5]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Let us clear the terminal.

Type

'''s '''''is equal to inside quotes''''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''''minus five''' gives '''W '''

Similarly we will get '''e '''<nowiki>for s[-10].</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[-15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''Since the string given to us is only 11 '''characters''' long.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>s[15]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Press Up arrow till we get '''x'''

'''x<nowiki>[0] = '</nowiki>B''''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''.

Let us clear the terminal.

Recall '''x'''

Press Enter

Let us manipulate '''x.'''

'''x '''''inside square brackets '''''zero '''''equal to inside quotes '''''B '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''Highlight the error'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error?

Initially the value of <nowiki>x[0] is ‘H’. </nowiki>

<nowiki>Now we are trying to assign another value ‘B’ to x[0].</nowiki>

Recall, strings cannot be modified after it is created.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions :

'''split()''' and''' join()'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is

'''str '''''dot join inside parentheses'' '''sequence'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

s = “-”seq = ("a", "b", "c"); print (s.join( seq ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Let us clear the terminal

Type

s ''is equal to inside quotes '''''hyphen '''press '''Enter'''seq ''is equal to inside parentheses '''''a '''''comma '''''b '''''comma '''''c '''press '''Enter'''

print s ''dot '''''join''''' inside parentheses'' '''seq '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c'''

It has joined a, b, c with hyphen.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide syntax for '''split()'''

str.split()
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is

'''str''' ''dot '''''split '''''open and close parentheses ''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal

str ''is equal to ''type as shown press '''Enter'''print '''str''' ''dot '''''split''' ''open and close parentheses''''' '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this.

It has split the string at spaces.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

In this tutorial, we have learnt to,''' '''

* Define strings in different ways.
* Concatenate strings.
* Print a string repeatedly.
* Access individual elements of the string.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Evaluation

# Write code to assign the string ' is called the apostrophe , to a variable s
# How will you change s='hello' to s='Hello'.
# The variables s and t are string and r is integer.

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r?

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# Write code to assign the string ''inside quotes ''is called the apostrophe , to variable s
# How will you change s ''is equal to '''hello' to s ''is equal to capital h '''Hello'.
# The variables s and t are strings and r is integer.

They are assigned with the values as shown below:

s=”Hello”

t=”World”

r=2

What is the output of s ''multiplied by'' r'' plus'' t ''multiplied by'' r?

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solutions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,''' '''

# The given string can be assigned in this manner
# Strings cannot be manipulated after it is assigned a value.

# The operation s ''multiplied by'' r'' plus'' t ''multiplied by'' r will print each of the two words twice as

'''HelloHelloWorldWorld '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-strings/English

2017-12-07T11:22:18Z

Trupti: Created page with "'''Python/C2/Getting Started with Strings/English'''<div style="margin-left:0cm;margin-right:0cm;">'''Title of script'''<..."

'''Python/C2/Getting Started with Strings/English'''<div style="margin-left:0cm;margin-right:0cm;">'''Title of script''': '''Getting Started with Strings'''</div>

<div style="margin-left:0cm;margin-right:0cm;">'''Author: Trupti Kini'''</div>

<div style="margin-left:0cm;margin-right:0cm;">'''Keywords: Python, Ipython'''</div><div style="margin-left:0cm;margin-right:0cm;"></div>

{| style="border-spacing:0;width:17.806cm;"
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
| align=center| '''Visual Cue'''
| align=center| '''Narration'''
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Show Slide 

containing title, name of the production team along with the logo of MHRD 
|| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''". 
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Show Slide 

Objectives 

|| At the end of this tutorial, you will learn to, 

# <div style="margin-left:1.27cm;margin-right:0cm;">Define strings in different ways. </div>
# <div style="margin-left:1.27cm;margin-right:0cm;">Concatenate strings. </div>
# <div style="margin-left:1.27cm;margin-right:0cm;">Print a string repeatedly. </div>
# <div style="margin-left:1.27cm;margin-right:0cm;">Access individual elements of the string. </div>

# <div style="margin-left:1.247cm;margin-right:0cm;">Learn immutability of strings. </div>

|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Show slide

System Specifications 
|| To record this tutorial, I am using * <div style="margin-left:1.27cm;margin-right:0cm;">'''Ubuntu Linux 16.04''' operating system</div>
* <div style="margin-left:1.27cm;margin-right:0cm;">'''Python 3.4.3'''</div>
* <div style="margin-left:1.27cm;margin-right:0cm;">'''IPython 5.1.0'''</div>

|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Show Slide 

Pre-requisites
|| To practise this tutorial, you should know how to * <div style="margin-left:1.27cm;margin-right:0cm;">run basic '''Python '''commands on the '''ipython console'''</div>

<div style="color:#000000;"></div>

If not, see the pre-requisite '''Python '''tutorials on this website.
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Show Slide 

What are Strings?

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

Example:

'This is a string'

“This is a string too”

‘’’This can be a large string’’’
|| What are '''strings'''? 

In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

For example: 

Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Show Slide

What are Strings?
|| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

We can also define empty '''strings'''.

'''String''' is an '''immutable''' '''collection'''.

That is, '''string''' cannot be '''modified''' after it is created.

'''String''' is a collection of characters which cannot be modified after it is created.
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;" | [Terminal]

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;" | Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.
|- style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"
|| [IPython console]

'''%pylab '''and press '''Enter.'''
|| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| [IPython Terminal]

'''a = 'Hello, World!' '''
|| We can assign a '''string''' to a '''variable '''called '''a.''' 

Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark'''

Press '''Enter'''
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| [IPython Terminal]

<div style="color:#000000;"></div>
|| Now let us learn string concatenation.

Let us assign strings to variables.
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| '''x = 'Hello' '''

'''y = 'World''''

'''z = x + ', ' + y + '!''''

'''print(z)'''
|| Type

'''x '''''is equal to inside quotes''''' Hello'''

Press '''Enter'''

'''y '''''is equal to inside quotes''''' World'''

Press '''Enter'''

Now, let us add the two strings.

'''z '''''is equal to '''''x '''''plus'' ''inside quotes''''' '''''comma''''' '''''plus''''' y '''''plus''''' '''''inside quotes '''''exclamation mark.'''

Press '''Enter'''

print ''inside parentheses'' '''z'''

Press '''Enter'''

Here '''x '''and '''y''' are '''string''' '''variables'''.

|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Highlight +
|| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''. 
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Highlight the output
|| Here we can see the output of string concatenation.
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| [IPython Terminal]

Press Up arrow till we get '''x'''

'''x * 5'''
|| What if we multiply a string with an integer?

Let us find out!

Type 

Recall''' x''' string.

Press '''Enter'''

'''x '''''multiplied by'' '''5'''

Press '''Enter'''
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Show Ipython Terminal 

Highlight the output
|| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''. 
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Show Slide

Exercise 1 
|| Pause the video. Try this exercise and then resume the video.

# <div style="margin-left:1.247cm;margin-right:0cm;">Obtain the '''string''' %% --------------------%% (20 '''hyphens''') without '''typing''' out all the twenty '''hyphens'''. </div>

|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| [IPython Terminal]

'''s = "%% " + "-"*20 + "%%"'''

'''print(s)'''
|| Switch to terminal for solution.

Type 

'''s '''''is equal to inside quotes''''' two percentages '''''plus inside quotes''''' hyphen '''''multiplied by''''' twenty''''' plus''''' '''''inside quotes''''' two percentages'''

Press '''Enter'''

'''print '''''inside parentheses '''''s'''

Press '''Enter'''
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
| style="color:#000000;" |
|| Let's now look at '''accessing''' individual '''elements''' of '''strings'''. 

We can access individual elements in the '''string''' using the '''subscripts.''' 
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| <div style="color:#000000;"></div>

[IPython Terminal]

Press Up arrow till we get '''a'''

'''a[0] '''

|| Recall '''a.'''

Type,

'''a '''''inside square brackets zero ''gives us the first '''character''' of the '''string'''. 

The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

where 'n' is the total number of '''characters''' in a '''string'''. 

We can '''access''' the '''strings''' from the end using '''negative''' '''indices.'''
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| [IPython Terminal]

'''a[-1] '''

'''a[-2]'''
|| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''!'''

'''a '''''inside square brackets '''''minus two''' gives us second '''element''' from the end of the '''string''' i.e. '''d'''
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| <div style="color:#000000;"></div>

Show Slide

Exercise 2

s = “Hello World”

what is the output of

'''s[-5]'''

'''s[-10]'''

'''s[-15] '''

'''s[15]'''

<div style="color:#000000;"></div>
|| Pause the video. Try this exercise and then resume the video.

Given a string, '''s''' which is '''Hello World''', what is the output of 

'''s[-5]'''

'''s[-10]'''

'''s[-15] '''

'''s[15]'''
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| [Ipython Terminal]

'''s = "Hello World”'''

'''s[-5]'''
|| Switch to the terminal.

Type

'''s '''''is equal to inside quotes''''' Hello World '''press '''Enter'''

'''s '''''inside square brackets '''''minus five''' gives us '''W '''

Similarly we will get '''e '''for s[-10].
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| [Ipython Terminal]

'''s[-15]''' 
|| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''Since the string given to us is only 11 '''characters''' long. 
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| [Ipython Terminal]

'''s[15]''' 
|| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| [Ipython Terminal]

Press Up arrow till we get '''x'''

'''x[0] = 'B''''

'''Highlight the error.'''
|| Let us attempt to change one of the '''characters''' in a '''string'''.

Type,

Recall '''x'''

Let us manipulate '''x.'''

'''x '''''inside square brackets '''''zero '''''equal to inside quotes '''''B '''press '''Enter'''

Why do we get an error?

Initially the value of x[0] is ‘H’. Now we are trying to assign another value ‘B’ to x[0].

Recall, strings cannot be modified after it is created.

We are trying to change the value of x[0] which was ‘'''H’ '''to''' B'.'''

We are getting added anan error because, '''strings''' are '''immutable''' and so cannot be manipulated.

|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Show slide
|| We can split and join the strings by using the functions :

split() and join()

|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Show slide

Syntax for''' join()'''

'''str.join(sequence)'''
||

To join a string

'''str '''''dot join inside parentheses'' '''sequence'''
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| [Ipython Terminal]

s = “-”seq = ("a", "b", "c"); print (s.join( seq ))

|| Switch to the terminal.

Type

s ''is equal to inside quotes '''''hyphen '''press '''Enter'''seq ''is equal to inside parentheses '''''a,b,c '''press '''Enter'''

print s ''dot '''''join''''' inside parentheses'' '''seq '''press '''Enter'''
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Highlight output
|| We will get output as '''a-b-c'''

It has joined a, b, c with hyphen.
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
||

Show slide syntax for '''split()'''

str.split()
|| To split a string

str ''dot ''split ''open and close parentheses ''
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| [Ipython Terminal]

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))

|| str ''is equal to ''"Line1-abcdef \nLine2-abc \nLine4-abcd" press '''Enter'''print str ''dot ''split ''open and close parentheses''''' '''press '''Enter'''
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Highlight output
|| We get the output '''['Line1-abcdef', 'Line2-abc', 'Line4-abcd']'''

It has split the string at spaces.
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Show Slide

Summary slide 

|| This brings us to the end of this tutorial. In this tutorial, we have learnt to,''' '''

# <div style="margin-left:1.247cm;margin-right:0cm;">Define '''strings''' in different ways. </div>

* <div style="margin-left:1.247cm;margin-right:0cm;">'''Concatenate''' '''strings''' by performing '''addition'''. </div>
* <div style="margin-left:1.247cm;margin-right:0cm;">Repeat a '''string''' 'n' number of times by doing '''multiplication'''. </div>
* <div style="margin-left:1.247cm;margin-right:0cm;">Access individual '''elements''' of the string by using their '''subscripts'''. </div>
* <div style="margin-left:1.247cm;margin-right:0cm;">Use the concept of '''immutability''' of '''strings'''. </div>
* <div style="margin-left:1.247cm;margin-right:0cm;">Define strings in different ways. </div>
* <div style="margin-left:1.247cm;margin-right:0cm;">Concatenate strings. </div>
* <div style="margin-left:1.247cm;margin-right:0cm;">Print a string repeatedly. </div>
* <div style="margin-left:1.247cm;margin-right:0cm;">Access individual elements of the string. </div>

|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Show Slide

Evaluation # <div style="margin-left:1.27cm;margin-right:0cm;">Write code to assign the string ' is called the apostrophe , to a variable s</div>
# <div style="margin-left:1.27cm;margin-right:0cm;">How will you change s='hello' to s='Hello'. </div>
# <div style="margin-left:1.27cm;margin-right:0cm;">Change the formatting as in visual cue.The variables s and t are string and r is integer.</div>

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r? 

|| Here are some self assessment questions for you to solve 

<div style="color:#000000;"></div># <div style="margin-left:1.27cm;margin-right:0cm;">Write code to assign the string ' is called the apostrophe , to variable s</div>
# <div style="margin-left:1.27cm;margin-right:0cm;">How will you change s='hello' to s='Hello'. </div>
# <div style="margin-left:1.27cm;margin-right:0cm;">The variables s and t are string and r is integer.</div>

They are assigned with the values as shown below:

s=”Hello”

t=”World”

r=2

What is the output of s * r + t * r? 

|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Show Slide

Solutions 

|| And the answers,''' '''# <div style="margin-left:1.247cm;margin-right:0cm;">The given string can be assigned in this manner </div>

s = " ` is called the apostrophe"

2.Strings cannot be manipulated after it is assigned a value.

3.The operation s * r + t * r will print each of the 

two words twice as

 HelloHelloWorldWorld 

|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
|| Show Slide

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Fossee Forum
|| Please post your general queries on Python in this forum.
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
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Textbook Companion
|| FOSSEE team coordinates the TBC project.
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Acknowledgment

http://spoken-tutorial.org
|| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.
|- style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"
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|| This is _________ from IIT Bombay signing off.

Thank you.
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<div style="margin-left:0cm;margin-right:0cm;"></div>

Python-3.4.3/C2/Getting-started-with-for/English

2017-11-15T10:51:27Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for''' loop.
# Use '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use lists.

If not, see the relevant Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
'''for''' statement iterates over the members of a sequence in order executing the block each time.

Here the loop variable takes the value of the item inside the sequence on each iteration.

For each '''item,''' the '''loop''' '''body''' is '''executed. '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''‘For’''' loop and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for''' loop. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the loop variable iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36

Note that here we used two variables,

* '''numbers -''' which is a list of numbers
* '''num''' - which is the element of list under consideration in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for''' '''statement''' '''indicates''' the starting of '''loop''' '''body'''.

Every '''statement '''in '''loop''' starts''' with 4 spaces'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single statement in the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for''' loop.

And the lines after that don't fall in the scope of the '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each block is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home '''directory'''.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal. Clear the terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your terminal.
Let us clear the terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as,

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

We get the square root of the given numbers executed by the for loop.

This is the print statement output executed after the for loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in sqrt_num_list.py

* Type each line of the code in the '''IPython''' '''interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Type,

'''numbers '''''equal to inside square brackets''''' 4, 9, 16, 25, 36''' and press enter

'''for num in numbers '''''colon''''' '''Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the prompt changes to three dots.

And the cursor is not after the three dots but, there are four spaces from the three dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the block.

The three dots tell you that you are inside a block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop''', '''print'' '''inside parentheses inside quotes sqrt of comma '''''num '''''comma inside quotes is comma''''' num '''''asterick asterick which is raised to power of''''' 0.5''' and press enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the statements in the block.

But still the interpreter is showing three dots, this means that you are still inside the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the block press '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the list, which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range '''built-in function in Python.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range ''''' ''''' start '''''comma '''''stop ''''' comma''''' step '''''
For example:

'''range '''''inside parentheses''''' one '''''comma''''' twenty '''''comma''''' two '''– generates integers from

1 to 19 with step of 2

'''range '''''inside parentheses''''' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the list.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten

Execute this in the '''Python''' interpreter.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for''' loop in a Python terminal window.

Open a new terminal by pressing Ctrl+alt+t keys simultaneously.

Start the '''Python''' '''interpreter''' by issuing the '''command''' '''python '''in the '''new terminal''' and press enter

Type,

'''for i '''in range ''inside parentheses''''' one '''''comma '''''eleven '''''colon''''' and '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python''' interpreter does not indent the code automatically.

So enter four spaces and then type the following

'''print'' '''''inside parentheses''''' ''i '''''comma inside quotes''' ''cube is '''''comma''''' i '''''raised to''''' '''''power of''''' three''' press enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit enter, we still see the three dots.

To get out of the block, press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! so the main thing we learnt here is -

* how to use the '''Python''' '''interpreter''' and

* the '''IPython''' interpreter to specify blocks.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython''' interpreter for ease of use.

The problem can be solved by just using the '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

for i in range(1, 50, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

Let us clear the terminal.

for''' i''' in '''range''' ''inside parentheses '''''one''' ''comma'' '''fifty''' ''comma''''' two''''' colon ''

print'' inside parentheses'' '''i''' press '''Enter '''twice

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight parameters in '''range '''function and highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate element.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create blocks in python using''' for'''
# Indent the blocks of code
# Iterate over a list using '''for''' loop
# Use the '''range()''' function

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for '''loop to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2.

'''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 i.e. [1,2,3,4]</nowiki>

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

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Acknowledgment

http://spoken-tutorial.org
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For more details, visit this website.

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Thank you.

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Python-3.4.3/C2/Getting-started-with-for/English

2017-11-15T10:48:56Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for''' loop.
# Use '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use lists.

If not, see the relevant Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
'''for''' statement iterates over the members of a sequence in order executing the block each time.

Here the loop variable takes the value of the item inside the sequence on each iteration.

For each '''item,''' the '''loop''' '''body''' is '''executed. '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''‘For’''' loop and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for''' loop. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the loop variable iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36

Note that here we used two variables,

* '''numbers -''' which is a list of numbers
* '''num''' - which is the element of list under consideration in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for''' '''statement''' '''indicates''' the starting of '''loop''' '''body'''.

Every '''statement '''in '''loop''' starts''' with 4 spaces'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single statement in the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for''' loop.

And the lines after that don't fall in the scope of the '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each block is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home '''directory'''.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal. Clear the terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your terminal.
Let us clear the terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as,

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

We get the square root of the given numbers executed by the for loop.

This is the print statement output executed after the for loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in sqrt_num_list.py

* Type each line of the code in the '''IPython''' '''interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Type,

'''numbers '''''equal to inside square brackets''''' 4, 9, 16, 25, 36''' and press enter

'''for num in numbers '''''colon''''' '''Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the prompt changes to three dots.

And the cursor is not after the three dots but, there are four spaces from the three dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the block.

The three dots tell you that you are inside a block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop''', '''print'' '''inside parentheses inside quotes sqrt of comma '''''num '''''comma inside quotes is comma''''' num '''''asterick asterick which is raised to power of''''' 0.5''' and press enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the statements in the block.

But still the interpreter is showing three dots, this means that you are still inside the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the block press '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the list, which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range '''built-in function in Python.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range ''''' ''''' start '''''comma '''''stop ''''' comma''''' step '''''
For example:

'''range '''''inside parentheses''''' one '''''comma''''' twenty '''''comma''''' two '''– generates integers from

1 to 19 with step of 2

'''range '''''inside parentheses''''' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the list.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten

Execute this in the '''Python''' interpreter.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for''' loop in a Python terminal window.

Open a new terminal by pressing Ctrl+alt+t keys simultaneously.

Start the '''Python''' '''interpreter''' by issuing the '''command''' '''python '''in the '''new terminal''' and press enter

Type,

'''for i '''in range ''inside parentheses''''' one '''''comma '''''eleven '''''colon''''' and '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python''' interpreter does not indent the code automatically.

So enter four spaces and then type the following

'''print'' '''''inside parentheses''''' ''i '''''comma inside quotes''' ''cube is '''''comma''''' i '''''raised to''''' '''''power of''''' three''' press enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit enter, we still see the three dots.

To get out of the block, press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! so the main thing we learnt here is -

* how to use the '''Python''' '''interpreter''' and

* the '''IPython''' interpreter to specify blocks.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython''' interpreter for ease of use.

The problem can be solved by just using the '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

for i in range(1, 50, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

Let us clear the terminal.

for''' i''' in '''range''' ''inside parentheses '''''one''' ''comma'' '''fifty''' ''comma''''' two''''' colon ''

print'' inside parentheses'' '''i''' press '''Enter '''twice

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight parameters in '''range '''function and highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate element.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create blocks in python using''' for'''
# Indent the blocks of code
# Iterate over a list using '''for''' loop
# Use the '''range()''' function

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for '''loop to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2.

'''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
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Thank you.

|}

Python-3.4.3/C2/Getting-started-with-for/English

2017-11-15T10:47:32Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for''' loop.
# Use '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use lists.

If not, see the relevant Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
'''for''' statement iterates over the members of a sequence in order executing the block each time.

Here the loop variable takes the value of the item inside the sequence on each iteration.

For each '''item,''' the '''loop''' '''body''' is '''executed. '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''‘For’''' loop and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for''' loop. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the loop variable iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36

Note that here we used two variables,

* '''numbers -''' which is a list of numbers
* '''num''' - which is the element of list under consideration in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for''' '''statement''' '''indicates''' the starting of '''loop''' '''body'''.

Every '''statement '''in '''loop''' starts''' with 4 spaces'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single statement in the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for''' loop.

And the lines after that don't fall in the scope of the '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each block is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home '''directory'''.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal. Clear the terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your terminal.
Let us clear the terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as,

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

We get the square root of the given numbers executed by the for loop.

This is the print statement output executed after the for loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in sqrt_num_list.py

* Type each line of the code in the '''IPython''' '''interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Type,

'''numbers '''''equal to inside square brackets''''' 4, 9, 16, 25, 36''' and press enter

'''for num in numbers '''''colon''''' '''Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the prompt changes to three dots.

And the cursor is not after the three dots but, there are four spaces from the three dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the block.

The three dots tell you that you are inside a block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop''', '''print'' '''inside parentheses inside quotes sqrt of comma '''''num '''''comma inside quotes is comma''''' num '''''asterick asterick which is raised to power of''''' 0.5''' and press enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the statements in the block.

But still the interpreter is showing three dots, this means that you are still inside the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the block press '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the list, which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range '''built-in function in Python.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range ''''' ''''' start '''''comma '''''stop ''''' comma''''' step '''''
For example:

'''range '''''inside parentheses''''' one '''''comma''''' twenty '''''comma''''' two '''– generates integers from

1 to 19 with step of 2

'''range '''''inside parentheses''''' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the list.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten

Execute this in the '''Python''' interpreter.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for''' loop in a Python terminal window.

Open a new terminal by pressing Ctrl+alt+t keys simultaneously.

Start the '''Python''' '''interpreter''' by issuing the '''command''' '''python '''in the '''new terminal''' and press enter

Type,

'''for i '''in range ''inside parentheses''''' one '''''comma '''''eleven '''''colon''''' and '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python''' interpreter does not indent the code automatically.

So enter four spaces and then type the following

'''print'' '''''inside parentheses''''' ''i '''''comma inside quotes''' ''cube is '''''comma''''' i '''''raised to''''' '''''power of''''' three''' press enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit enter, we still see the three dots.

To get out of the block, press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! so the main thing we learnt here is -

* how to use the '''Python''' '''interpreter''' and

* the '''IPython''' interpreter to specify blocks.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython''' interpreter for ease of use.

The problem can be solved by just using the '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

for i in range(1, 50, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

Let us clear the terminal.

for''' i''' in '''range''' ''inside parentheses '''''one''' ''comma'' '''fifty''' ''comma''''' two''''' colon ''

print'' inside parentheses'' '''i''' and press '''Enter '''twice

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight parameters in '''range '''function and highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate element.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create blocks in python using''' for'''
# Indent the blocks of code
# Iterate over a list using '''for''' loop
# Use the '''range()''' function

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for '''loop to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2.

'''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
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Thank you.

|}

Python-3.4.3/C2/Getting-started-with-for/English

2017-11-15T10:37:56Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for''' loop.
# Use '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use lists.

If not, see the relevant Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
'''for''' statement iterates over the members of a sequence in order executing the block each time.

Here the loop variable takes the value of the item inside the sequence on each iteration.

For each '''item,''' the '''loop''' '''body''' is '''executed. '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''‘For’''' loop and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for''' loop. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the loop variable iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36

Note that here we used two variables,

* '''numbers -''' which is a list of numbers
* '''num''' - which is the element of list under consideration in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for''' '''statement''' '''indicates''' the starting of '''loop''' '''body'''.

Every '''statement '''in '''loop''' starts''' with 4 spaces'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single statement in the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for''' loop.

And the lines after that don't fall in the scope of the '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each block is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home '''directory'''.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal. Clear the terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your terminal.
Let us clear the terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as,

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

We get the square root of the given numbers executed by the for loop.

This is the print statement output executed after the for loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in sqrt_num_list.py

* Type each line of the code in the '''IPython''' '''interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Type,

'''numbers '''''equal to inside square brackets''''' 4, 9, 16, 25, 36''' and press enter

'''for num in numbers '''''colon''''' '''Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the prompt changes to three dots.

And the cursor is not after the three dots but, there are four spaces from the three dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the block.

The three dots tell you that you are inside a block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop''', '''print'' '''inside parentheses inside quotes sqrt of comma '''''num '''''comma inside quotes is comma''''' num '''''asterick asterick which is raised to power of''''' 0.5''' and press enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the statements in the block.

But still the interpreter is showing three dots, this means that you are still inside the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the block press '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the list, which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range '''built-in function in Python.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range ''''' ''''' start '''''comma '''''stop ''''' comma''''' step '''''
For example:

'''range '''''inside parentheses''''' one '''''comma''''' twenty '''''comma''''' two '''– generates integers from

1 to 19 with step of 2

'''range '''''inside parentheses''''' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the list.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten

Execute this in the '''Python''' interpreter.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for''' loop in a Python terminal window.

Open a new terminal by pressing Ctrl+alt+t keys simultaneously.

Start the '''Python''' '''interpreter''' by issuing the '''command''' '''python '''in the '''new terminal''' and press enter

Type,

'''for i '''in range ''inside parentheses''''' one '''''comma '''''eleven '''''colon''''' and '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python''' interpreter does not indent the code automatically.

So enter four spaces and then type the following

'''print'' '''''inside parentheses''''' ''i '''''comma inside quotes''' ''cube is '''''comma''''' i '''''raised to''''' '''''power of''''' three'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit enter, we still see the three dots.

To get out of the block, press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! so the main thing we learnt here is -

* how to use the '''Python''' '''interpreter''' and

* the '''IPython''' interpreter to specify blocks.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython''' interpreter for ease of use.

The problem can be solved by just using the '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

for i in range(1, 50, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

Let us clear the terminal.

for''' i''' in '''range''' ''inside parentheses '''''one''' ''comma'' '''fifty''' ''comma''''' two''''' colon ''

print'' inside parentheses'' '''i''' and press '''Enter '''twice

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight parameters in '''range '''function and highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate element.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create blocks in python using''' for'''
# Indent the blocks of code
# Iterate over a list using '''for''' loop
# Use the '''range()''' function

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for '''loop to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2.

'''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-for/English

2017-11-15T10:34:46Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for''' loop.
# Use '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use lists.

If not, see the relevant Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
'''for''' statement iterates over the members of a sequence in order executing the block each time.

Here the loop variable takes the value of the item inside the sequence on each iteration.

For each '''item,''' the '''loop''' '''body''' is '''executed. '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''‘For’''' loop and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for''' loop. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the loop variable iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36

Note that here we used two variables,

* '''numbers -''' which is a list of numbers
* '''num''' - which is the element of list under consideration in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for''' '''statement''' '''indicates''' the starting of '''loop''' '''body'''.

Every '''statement '''in '''loop''' starts''' with 4 spaces'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single statement in the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for''' loop.

And the lines after that don't fall in the scope of the '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each block is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home '''directory'''.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal. Clear the terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your terminal.
Let us clear the terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as,

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

We get the square root of the given numbers executed by the for loop.

This is the print statement output executed after the for loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in sqrt_num_list.py

* Type each line of the code in the '''IPython''' '''interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Type,

'''numbers '''''equal to inside square brackets''''' 4, 9, 16, 25, 36''' and press enter

'''for num in numbers '''''colon''''' '''Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the prompt changes to three dots.

And the cursor is not after the three dots but, there are four spaces from the three dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the block.

The three dots tell you that you are inside a block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop''', '''print'' '''inside parentheses inside quotes sqrt of comma '''''num '''''comma inside quotes is comma''''' num '''''asterick asterick which is raised to power of''''' 0.5''' and press enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the statements in the block.

But still the interpreter is showing three dots, this means that you are still inside the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the block press '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the list, which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range '''built-in function in Python.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range ''''' ''''' start '''''comma '''''stop ''''' comma''''' step '''''
For example:

'''range '''''inside parentheses''''' one '''''comma''''' twenty '''''comma''''' two '''– generates integers from

1 to 19 with step of 2

'''range '''''inside parentheses''''' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the list.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten

Execute this in the '''Python''' interpreter.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for''' loop in a Python terminal window.

Open a new terminal by pressing Ctrl+alt+t keys simultaneously.

Start the '''Python''' '''interpreter''' by issuing the '''command''' '''python '''in the '''new terminal''' and press enter

Type,

'''for i '''in range ''inside parentheses''''' one '''''comma '''''eleven '''''colon''''' and '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python''' interpreter does not indent the code automatically.

So enter four spaces and then type the following

'''print'' '''''inside parentheses''''' ''i '''''comma inside quotes''' ''cube is '''''comma''''' i '''''raised to''''' '''''power of''''' three'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit enter, we still see the three dots.

To get out of the block, press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! so the main thing we learnt here is -

* how to use the '''Python''' '''interpreter''' and

* the '''IPython''' interpreter to specify blocks.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython''' interpreter for ease of use.

The problem can be solved by just using the '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

for i in range(1, 51, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|

Let us clear the terminal.

for''' i''' in '''range''' ''inside parentheses '''''one''' ''comma'' '''fifty one''' ''comma''''' two''''' colon ''

print'' inside parentheses'' '''i''' and press '''Enter '''twice

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight parameters in '''range '''function and highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate element.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create blocks in python using''' for'''
# Indent the blocks of code
# Iterate over a list using '''for''' loop
# Use the '''range()''' function

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for '''loop to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2.

'''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-for/English

2017-11-15T10:20:21Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for''' loop.
# Use '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use lists.

If not, see the relevant Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
'''for''' statement iterates over the members of a sequence in order executing the block each time.

Here the loop variable takes the value of the item inside the sequence on each iteration.

For each '''item,''' the '''loop''' '''body''' is '''executed. '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''‘For’''' loop and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for''' loop. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the loop variable iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36

Note that here we used two variables,

* '''numbers -''' which is a list of numbers
* '''num''' - which is the element of list under consideration in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for''' '''statement''' '''indicates''' the starting of '''loop''' '''body'''.

Every '''statement '''in '''loop''' starts''' with 4 spaces'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single statement in the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for''' loop.

And the lines after that don't fall in the scope of the '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each block is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home '''directory'''.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal. Clear the terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your terminal.
Let us clear the terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as,

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

We get the square root of the given numbers executed by the for loop.

This is the print statement output executed after the for loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in sqrt_num_list.py

* Type each line of the code in the '''IPython''' '''interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Type,

'''numbers '''''equal to inside square brackets''''' 4, 9, 16, 25, 36''' and press enter

'''for num in numbers '''''colon''''' '''Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the prompt changes to three dots.

And the cursor is not after the three dots but, there are four spaces from the three dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the block.

The three dots tell you that you are inside a block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop''', '''print'' '''inside parentheses inside quotes sqrt of comma '''''num '''''comma inside quotes is comma''''' num '''''asterick asterick which is raised to power of''''' 0.5''' and press enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the statements in the block.

But still the interpreter is showing three dots, this means that you are still inside the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the block press '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the list, which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range '''built-in function in Python.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range ''''' ''''' start '''''comma '''''stop ''''' comma''''' step '''''
For example:

'''range '''''inside parentheses''''' one '''''comma''''' twenty '''''comma''''' two '''– generates integers from

1 to 19 with step of 2

'''range '''''inside parentheses''''' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the list.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten

Execute this in the '''Python''' interpreter.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for''' loop in a Python terminal window.

Open a new terminal by pressing Ctrl+alt+t keys simultaneously.

Start the '''Python''' '''interpreter''' by issuing the '''command''' '''python '''in the '''new terminal''' and press enter

Type,

'''for i '''in range ''inside parentheses''''' one '''''comma '''''eleven '''''colon''''' and '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python''' interpreter does not indent the code automatically.

So enter four spaces and then type the following

'''print'' '''''inside parentheses''''' ''i '''''comma inside quotes''' ''cube is '''''comma''''' i '''''raised to''''' '''''power of''''' three'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit enter, we still see the three dots.

To get out of the block, press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! so the main thing we learnt here is -

* how to use the '''Python''' '''interpreter''' and

* the '''IPython''' interpreter to specify blocks.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython''' interpreter for ease of use.

The problem can be solved by just using the '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

for i in range(1, 51, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| for''' i''' in '''range''' ''inside parentheses '''''one''' ''comma'' '''fifty one''' ''comma''''' two''''' colon ''

print'' inside parentheses'' '''i''' and press '''Enter '''twice

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight parameters in '''range '''function and highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate element.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create blocks in python using''' for'''
# Indent the blocks of code
# Iterate over a list using '''for''' loop
# Use the '''range()''' function

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for '''loop to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2.

'''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-for/English

2017-11-15T10:15:00Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for''' loop.
# Use '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use lists.

If not, see the relevant Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
'''for''' statement iterates over the members of a sequence in order executing the block each time.

Here the loop variable takes the value of the item inside the sequence on each iteration.

For each '''item,''' the '''loop''' '''body''' is '''executed. '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''‘For’''' loop and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for''' loop. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the loop variable iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36

Note that here we used two variables,

* '''numbers -''' which is a list of numbers
* '''num''' - which is the element of list under consideration in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for''' '''statement''' '''indicates''' the starting of '''loop''' '''body'''.

Every '''statement '''in '''loop''' starts''' with 4 spaces'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single statement in the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for''' loop.

And the lines after that don't fall in the scope of the '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each block is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home '''directory'''.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal. Clear the terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your terminal.
Let us clear the terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as,

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

We get the square root of the given numbers executed by the for loop.

This is the print statement output executed after the for loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in sqrt_num_list.py

* Type each line of the code in the '''IPython''' '''interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Type,

'''numbers '''''equal to inside square brackets''''' 4, 9, 16, 25, 36''' and press enter

'''for num in numbers '''''colon''''' '''Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the prompt changes to three dots.

And the cursor is not after the three dots but, there are four spaces from the three dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the block.

The three dots tell you that you are inside a block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop''', '''print'' '''inside parentheses inside quotes sqrt of comma '''''num '''''comma inside quotes is comma''''' num '''''asterick asterick which is raised to power of''''' 0.5''' and press enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the statements in the block.

But still the interpreter is showing three dots, this means that you are still inside the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the block press '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the list, which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range '''built-in function in Python.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range ''''' ''''' start '''''comma '''''stop ''''' comma''''' step '''''close square brackets''

For example:

'''range '''''inside parentheses''''' one '''''comma''''' twenty '''''comma''''' two '''– generates integers from

1 to 19 with step of 2

'''range '''''inside parentheses''''' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the list.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten

Execute this in the '''Python''' interpreter.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for''' loop in a Python terminal window.

Start the '''Python''' '''interpreter''' by issuing the '''command''' '''python '''in a '''new terminal'''.

Type,

'''for i '''in range ''inside parentheses''''' one '''''comma '''''eleven '''''colon''''' '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python''' interpreter does not indent the code automatically.

So enter four spaces there and then type the following

'''print'' '''''inside parentheses''''' ''i '''''comma inside quotes''' ''cube is '''''comma''''' i '''''raised to''''' '''''power of''''' three'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit enter, we still see the three dots.

To get out of the block, press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! so the main thing we learnt here is -

* how to use the '''Python''' '''interpreter''' and

* the '''IPython''' interpreter to specify blocks.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython''' interpreter for ease of use.

The problem can be solved by just using the '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

for i in range(1, 51, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| for''' i''' in '''range''' ''inside parentheses '''''one''' ''comma'' '''fifty one''' ''comma''''' two''''' colon ''

print'' inside parentheses'' '''i''' and press '''Enter '''twice

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight parameters in '''range '''function and highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate element.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create blocks in python using''' for'''
# Indent the blocks of code
# Iterate over a list using '''for''' loop
# Use the '''range()''' function

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for '''loop to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2.

'''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-for/English

2017-11-15T10:12:25Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for''' loop.
# Use '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use lists.

If not, see the relevant Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
'''for''' statement iterates over the members of a sequence in order executing the block each time.

Here the loop variable takes the value of the item inside the sequence on each iteration.

For each '''item,''' the '''loop''' '''body''' is '''executed. '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''‘For’''' loop and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for''' loop. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the loop variable iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36

Note that here we used two variables,

* '''numbers -''' which is a list of numbers
* '''num''' - which is the element of list under consideration in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for''' '''statement''' '''indicates''' the starting of '''loop''' '''body'''.

Every '''statement '''in '''loop''' starts''' with 4 spaces'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single statement in the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for''' loop.

And the lines after that don't fall in the scope of the '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each block is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home '''directory'''.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal. Clear the terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your terminal.
Let us clear the terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as,

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

We get the square root of the given numbers executed by the for loop.

This is the print statement output executed after the for loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in sqrt_num_list.py

* Type each line of the code in the '''IPython''' '''interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Type,

'''numbers '''''equal to inside square brackets''''' 4, 9, 16, 25, 36''' and press enter

'''for num in numbers '''''colon''''' '''Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the prompt changes to three dots.

And the cursor is not after the three dots but, there are four spaces from the three dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the block.

The three dots tell you that you are inside a block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop''', '''print'' '''inside parentheses inside quotes sqrt of comma '''''num '''''comma inside quotes is comma''''' num '''''asterick asterick which is raised to power of''''' 0.5''' and press enter

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the statements in the block.

But still the interpreter is showing three dots, this means that you are still inside the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the block press the '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the list, which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range '''built-in function in Python.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range '''''inside parentheses inside square brackets''''' start '''''comma close square brackets '''''stop '''''open square brackets comma''''' step '''''close square brackets''

For example:

'''range '''''inside parentheses''''' one '''''comma''''' twenty '''''comma''''' two '''– generates integers from

1 to 19 with step of 2

'''range '''''inside parentheses''''' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the list.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten

Execute this in the '''Python''' interpreter.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for''' loop in a Python terminal window.

Start the '''Python''' '''interpreter''' by issuing the '''command''' '''python '''in a '''new terminal'''.

Type,

'''for i '''in range ''inside parentheses''''' one '''''comma '''''eleven '''''colon''''' '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python''' interpreter does not indent the code automatically.

So enter four spaces there and then type the following

'''print'' '''''inside parentheses''''' ''i '''''comma inside quotes''' ''cube is '''''comma''''' i '''''raised to''''' '''''power of''''' three'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit enter, we still see the three dots.

To get out of the block, press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! so the main thing we learnt here is -

* how to use the '''Python''' '''interpreter''' and

* the '''IPython''' interpreter to specify blocks.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython''' interpreter for ease of use.

The problem can be solved by just using the '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

for i in range(1, 51, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| for''' i''' in '''range''' ''inside parentheses '''''one''' ''comma'' '''fifty one''' ''comma''''' two''''' colon ''

print'' inside parentheses'' '''i''' and press '''Enter '''twice

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight parameters in '''range '''function and highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate element.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create blocks in python using''' for'''
# Indent the blocks of code
# Iterate over a list using '''for''' loop
# Use the '''range()''' function

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for '''loop to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2.

'''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-for/English

2017-11-15T10:09:20Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for''' loop.
# Use '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use lists.

If not, see the relevant Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
'''for''' statement iterates over the members of a sequence in order executing the block each time.

Here the loop variable takes the value of the item inside the sequence on each iteration.

For each '''item,''' the '''loop''' '''body''' is '''executed. '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''‘For’''' loop and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for''' loop. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the loop variable iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36

Note that here we used two variables,

* '''numbers -''' which is a list of numbers
* '''num''' - which is the element of list under consideration in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for''' '''statement''' '''indicates''' the starting of '''loop''' '''body'''.

Every '''statement '''in '''loop''' starts''' with 4 spaces'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single statement in the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for''' loop.

And the lines after that don't fall in the scope of the '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each block is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home '''directory'''.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal. Clear the terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your terminal.
Let us clear the terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as,

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

We get the square root of the given numbers executed by the for loop.

This is the print statement output executed after the for loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in sqrt_num_list.py

* Type each line of the code in the '''IPython''' '''interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Type,

'''numbers '''''equal to inside square brackets''''' 4, 9, 16, 25, 36''' and press enter

'''for num in numbers '''''colon''''' '''Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the prompt changes to three dots.

And the cursor is not after the three dots but, there are four spaces from the three dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the block.

The three dots tell you that you are inside a block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop''', '''print'' '''inside parentheses inside quotes sqrt of comma '''''num '''''comma inside quotes is comma''''' num '''''raised to power of''''' 0.5'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the statements in the block.

But still the interpreter is showing three dots, this means that you are still inside the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the block press the '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the list, which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range '''built-in function in Python.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range '''''inside parentheses inside square brackets''''' start '''''comma close square brackets '''''stop '''''open square brackets comma''''' step '''''close square brackets''

For example:

'''range '''''inside parentheses''''' one '''''comma''''' twenty '''''comma''''' two '''– generates integers from

1 to 19 with step of 2

'''range '''''inside parentheses''''' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the list.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten

Execute this in the '''Python''' interpreter.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for''' loop in a Python terminal window.

Start the '''Python''' '''interpreter''' by issuing the '''command''' '''python '''in a '''new terminal'''.

Type,

'''for i '''in range ''inside parentheses''''' one '''''comma '''''eleven '''''colon''''' '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python''' interpreter does not indent the code automatically.

So enter four spaces there and then type the following

'''print'' '''''inside parentheses''''' ''i '''''comma inside quotes''' ''cube is '''''comma''''' i '''''raised to''''' '''''power of''''' three'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit enter, we still see the three dots.

To get out of the block, press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! so the main thing we learnt here is -

* how to use the '''Python''' '''interpreter''' and

* the '''IPython''' interpreter to specify blocks.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython''' interpreter for ease of use.

The problem can be solved by just using the '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

for i in range(1, 51, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| for''' i''' in '''range''' ''inside parentheses '''''one''' ''comma'' '''fifty one''' ''comma''''' two''''' colon ''

print'' inside parentheses'' '''i''' and press '''Enter '''twice

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight parameters in '''range '''function and highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate element.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create blocks in python using''' for'''
# Indent the blocks of code
# Iterate over a list using '''for''' loop
# Use the '''range()''' function

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for '''loop to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2.

'''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-for/English

2017-11-15T10:04:11Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for''' loop.
# Use '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use lists.

If not, see the relevant Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
'''for''' statement iterates over the members of a sequence in order executing the block each time.

Here the loop variable takes the value of the item inside the sequence on each iteration.

For each '''item,''' the '''loop''' '''body''' is '''executed. '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''‘For’''' loop and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for''' loop. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the loop variable iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36

Note that here we used two variables,

* '''numbers -''' which is a list of numbers
* '''num''' - which is the element of list under consideration in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for''' '''statement''' '''indicates''' the starting of '''loop''' '''body'''.

Every '''statement '''in '''loop''' starts''' with 4 spaces'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single statement in the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for''' loop.

And the lines after that don't fall in the scope of the '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each block is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home '''directory'''.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal. Clear the terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your terminal.
Let us clear the terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as,

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

We get the square root of the given numbers executed by the for loop.

This is the print statement output executed after the for loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in sqrt_num_list.py

* Type each line of the code in the '''IPython''' '''interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Type,

'''numbers '''''equal to inside square brackets''''' 4, 9, 16, 25, 36'''

'''for num in numbers '''''colon''''' '''Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the prompt changes to three dots.

And the cursor is not right after the three dots but, there are four spaces from the dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the block.

The three dots tell you that you are inside a block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop''', '''print'' '''inside parentheses inside quotes sqrt of comma '''''num '''''comma inside quotes is comma''''' num '''''raised to power of''''' 0.5'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the statements in the block.

But still the interpreter is showing three dots, this means that you are still inside the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the block press the '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the list, which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range '''built-in function in Python.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range '''''inside parentheses inside square brackets''''' start '''''comma close square brackets '''''stop '''''open square brackets comma''''' step '''''close square brackets''

For example:

'''range '''''inside parentheses''''' one '''''comma''''' twenty '''''comma''''' two '''– generates integers from

1 to 19 with step of 2

'''range '''''inside parentheses''''' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the list.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten

Execute this in the '''Python''' interpreter.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for''' loop in a Python terminal window.

Start the '''Python''' '''interpreter''' by issuing the '''command''' '''python '''in a '''new terminal'''.

Type,

'''for i '''in range ''inside parentheses''''' one '''''comma '''''eleven '''''colon''''' '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python''' interpreter does not indent the code automatically.

So enter four spaces there and then type the following

'''print'' '''''inside parentheses''''' ''i '''''comma inside quotes''' ''cube is '''''comma''''' i '''''raised to''''' '''''power of''''' three'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit enter, we still see the three dots.

To get out of the block, press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! so the main thing we learnt here is -

* how to use the '''Python''' '''interpreter''' and

* the '''IPython''' interpreter to specify blocks.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython''' interpreter for ease of use.

The problem can be solved by just using the '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

for i in range(1, 51, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| for''' i''' in '''range''' ''inside parentheses '''''one''' ''comma'' '''fifty one''' ''comma''''' two''''' colon ''

print'' inside parentheses'' '''i''' and press '''Enter '''twice

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight parameters in '''range '''function and highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate element.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create blocks in python using''' for'''
# Indent the blocks of code
# Iterate over a list using '''for''' loop
# Use the '''range()''' function

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for '''loop to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2.

'''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-for/English

2017-11-15T10:03:10Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for''' loop.
# Use '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use lists.

If not, see the relevant Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
'''for''' statement iterates over the members of a sequence in order executing the block each time.

Here the loop variable takes the value of the item inside the sequence on each iteration.

For each '''item,''' the '''loop''' '''body''' is '''executed. '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''‘For’''' loop and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for''' loop. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the loop variable iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36

Note that here we used two variables,

* '''numbers -''' which is a list of numbers
* '''num''' - which is the element of list under consideration in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for''' '''statement''' '''indicates''' the starting of '''loop''' '''body'''.

Every '''statement '''in '''loop''' starts''' with 4 spaces'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single statement in the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for''' loop.

And the lines after that don't fall in the scope of the '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each block is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home '''directory'''.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your terminal.
Let us clear the terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as,

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

We get the square root of the given numbers executed by the for loop.

This is the print statement output executed after the for loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in sqrt_num_list.py

* Type each line of the code in the '''IPython''' '''interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Type,

'''numbers '''''equal to inside square brackets''''' 4, 9, 16, 25, 36'''

'''for num in numbers '''''colon''''' '''Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the prompt changes to three dots.

And the cursor is not right after the three dots but, there are four spaces from the dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the block.

The three dots tell you that you are inside a block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop''', '''print'' '''inside parentheses inside quotes sqrt of comma '''''num '''''comma inside quotes is comma''''' num '''''raised to power of''''' 0.5'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the statements in the block.

But still the interpreter is showing three dots, this means that you are still inside the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the block press the '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the list, which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range '''built-in function in Python.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range '''''inside parentheses inside square brackets''''' start '''''comma close square brackets '''''stop '''''open square brackets comma''''' step '''''close square brackets''

For example:

'''range '''''inside parentheses''''' one '''''comma''''' twenty '''''comma''''' two '''– generates integers from

1 to 19 with step of 2

'''range '''''inside parentheses''''' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the list.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten

Execute this in the '''Python''' interpreter.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for''' loop in a Python terminal window.

Start the '''Python''' '''interpreter''' by issuing the '''command''' '''python '''in a '''new terminal'''.

Type,

'''for i '''in range ''inside parentheses''''' one '''''comma '''''eleven '''''colon''''' '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python''' interpreter does not indent the code automatically.

So enter four spaces there and then type the following

'''print'' '''''inside parentheses''''' ''i '''''comma inside quotes''' ''cube is '''''comma''''' i '''''raised to''''' '''''power of''''' three'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit enter, we still see the three dots.

To get out of the block, press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! so the main thing we learnt here is -

* how to use the '''Python''' '''interpreter''' and

* the '''IPython''' interpreter to specify blocks.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython''' interpreter for ease of use.

The problem can be solved by just using the '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

for i in range(1, 51, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| for''' i''' in '''range''' ''inside parentheses '''''one''' ''comma'' '''fifty one''' ''comma''''' two''''' colon ''

print'' inside parentheses'' '''i''' and press '''Enter '''twice

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight parameters in '''range '''function and highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate element.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create blocks in python using''' for'''
# Indent the blocks of code
# Iterate over a list using '''for''' loop
# Use the '''range()''' function

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for '''loop to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2.

'''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-for/English

2017-11-15T09:59:58Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for''' loop.
# Use '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use lists.

If not, see the relevant Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
'''for''' statement iterates over the members of a sequence in order executing the block each time.

Here the loop variable takes the value of the item inside the sequence on each iteration.

For each '''item,''' the '''loop''' '''body''' is '''executed. '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''‘For’''' loop and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for''' loop. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the loop variable iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36

Note that here we used two variables,

* '''numbers -''' which is a list of numbers
* '''num''' - which is the element of list under consideration in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for''' '''statement''' '''indicates''' the starting of '''loop''' '''body'''.

Every '''statement '''in '''loop''' starts''' with 4 spaces'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single statement in the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for''' loop.

And the lines after that don't fall in the scope of the '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each block is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home '''directory'''.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as,

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

We get the square root of the given numbers executed by the for loop.

This is the print statement output executed after the for loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in sqrt_num_list.py

* Type each line of the code in the '''IPython''' '''interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Type,

'''numbers '''''equal to inside square brackets''''' 4, 9, 16, 25, 36'''

'''for num in numbers '''''colon''''' '''Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the prompt changes to three dots.

And the cursor is not right after the three dots but, there are four spaces from the dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the block.

The three dots tell you that you are inside a block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop''', '''print'' '''inside parentheses inside quotes sqrt of comma '''''num '''''comma inside quotes is comma''''' num '''''raised to power of''''' 0.5'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the statements in the block.

But still the interpreter is showing three dots, this means that you are still inside the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the block press the '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the list, which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range '''built-in function in Python.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range '''''inside parentheses inside square brackets''''' start '''''comma close square brackets '''''stop '''''open square brackets comma''''' step '''''close square brackets''

For example:

'''range '''''inside parentheses''''' one '''''comma''''' twenty '''''comma''''' two '''– generates integers from

1 to 19 with step of 2

'''range '''''inside parentheses''''' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the list.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten

Execute this in the '''Python''' interpreter.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for''' loop in a Python terminal window.

Start the '''Python''' '''interpreter''' by issuing the '''command''' '''python '''in a '''new terminal'''.

Type,

'''for i '''in range ''inside parentheses''''' one '''''comma '''''eleven '''''colon''''' '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python''' interpreter does not indent the code automatically.

So enter four spaces there and then type the following

'''print'' '''''inside parentheses''''' ''i '''''comma inside quotes''' ''cube is '''''comma''''' i '''''raised to''''' '''''power of''''' three'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit enter, we still see the three dots.

To get out of the block, press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! so the main thing we learnt here is -

* how to use the '''Python''' '''interpreter''' and

* the '''IPython''' interpreter to specify blocks.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython''' interpreter for ease of use.

The problem can be solved by just using the '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

for i in range(1, 51, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| for''' i''' in '''range''' ''inside parentheses '''''one''' ''comma'' '''fifty one''' ''comma''''' two''''' colon ''

print'' inside parentheses'' '''i''' and press '''Enter '''twice

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight parameters in '''range '''function and highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate element.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create blocks in python using''' for'''
# Indent the blocks of code
# Iterate over a list using '''for''' loop
# Use the '''range()''' function

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for '''loop to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2.

'''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-for/English

2017-11-15T09:53:23Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for''' loop.
# Use '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use lists.

If not, see the relevant Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
'''for''' statement iterates over the members of a sequence in order executing the block each time.

Here the loop variable takes the value of the item inside the sequence on each iteration.

For each '''item,''' the '''loop''' '''body''' is '''executed. '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''‘For’''' loop and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for''' loop. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the '''for''' loop iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36

Note that here we used two variables,

* '''numbers -''' which is a list of numbers
* '''num''' - which is the element of list under consideration in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for''' '''statement''' '''indicates''' the starting of '''loop''' '''body'''.

Every '''statement '''in '''loop''' starts''' with 4 spaces'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single statement in the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for''' loop.

And the lines after that don't fall in the scope of the '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each block is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home '''directory'''.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as,

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

We get the square root of the given numbers executed by the for loop.

This is the print statement output executed after the for loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in sqrt_num_list.py

* Type each line of the code in the '''IPython''' '''interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Type,

'''numbers '''''equal to inside square brackets''''' 4, 9, 16, 25, 36'''

'''for num in numbers '''''colon''''' '''Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the prompt changes to three dots.

And the cursor is not right after the three dots but, there are four spaces from the dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the block.

The three dots tell you that you are inside a block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop''', '''print'' '''inside parentheses inside quotes sqrt of comma '''''num '''''comma inside quotes is comma''''' num '''''raised to power of''''' 0.5'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the statements in the block.

But still the interpreter is showing three dots, this means that you are still inside the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the block press the '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the list, which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range '''built-in function in Python.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range '''''inside parentheses inside square brackets''''' start '''''comma close square brackets '''''stop '''''open square brackets comma''''' step '''''close square brackets''

For example:

'''range '''''inside parentheses''''' one '''''comma''''' twenty '''''comma''''' two '''– generates integers from

1 to 19 with step of 2

'''range '''''inside parentheses''''' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the list.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten

Execute this in the '''Python''' interpreter.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for''' loop in a Python terminal window.

Start the '''Python''' '''interpreter''' by issuing the '''command''' '''python '''in a '''new terminal'''.

Type,

'''for i '''in range ''inside parentheses''''' one '''''comma '''''eleven '''''colon''''' '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python''' interpreter does not indent the code automatically.

So enter four spaces there and then type the following

'''print'' '''''inside parentheses''''' ''i '''''comma inside quotes''' ''cube is '''''comma''''' i '''''raised to''''' '''''power of''''' three'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit enter, we still see the three dots.

To get out of the block, press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! so the main thing we learnt here is -

* how to use the '''Python''' '''interpreter''' and

* the '''IPython''' interpreter to specify blocks.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython''' interpreter for ease of use.

The problem can be solved by just using the '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

for i in range(1, 51, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| for''' i''' in '''range''' ''inside parentheses '''''one''' ''comma'' '''fifty one''' ''comma''''' two''''' colon ''

print'' inside parentheses'' '''i''' and press '''Enter '''twice

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight parameters in '''range '''function and highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate element.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create blocks in python using''' for'''
# Indent the blocks of code
# Iterate over a list using '''for''' loop
# Use the '''range()''' function

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for '''loop to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2.

'''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-for/English

2017-11-15T09:52:39Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for''' loop.
# Use '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use lists.

If not, see the relevant Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
'''for''' statement iterates over the members of a sequence in order executing the block each time.
Here the loop variable takes the value of the item inside the sequence on each iteration.
For each '''item,''' the '''loop''' '''body''' is '''executed. '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''‘For’''' loop and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for''' loop. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the '''for''' loop iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36

Note that here we used two variables,

* '''numbers -''' which is a list of numbers
* '''num''' - which is the element of list under consideration in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for''' '''statement''' '''indicates''' the starting of '''loop''' '''body'''.

Every '''statement '''in '''loop''' starts''' with 4 spaces'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single statement in the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for''' loop.

And the lines after that don't fall in the scope of the '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each block is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home '''directory'''.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as,

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

We get the square root of the given numbers executed by the for loop.

This is the print statement output executed after the for loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in sqrt_num_list.py

* Type each line of the code in the '''IPython''' '''interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Type,

'''numbers '''''equal to inside square brackets''''' 4, 9, 16, 25, 36'''

'''for num in numbers '''''colon''''' '''Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the prompt changes to three dots.

And the cursor is not right after the three dots but, there are four spaces from the dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the block.

The three dots tell you that you are inside a block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop''', '''print'' '''inside parentheses inside quotes sqrt of comma '''''num '''''comma inside quotes is comma''''' num '''''raised to power of''''' 0.5'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the statements in the block.

But still the interpreter is showing three dots, this means that you are still inside the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the block press the '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the list, which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range '''built-in function in Python.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range '''''inside parentheses inside square brackets''''' start '''''comma close square brackets '''''stop '''''open square brackets comma''''' step '''''close square brackets''

For example:

'''range '''''inside parentheses''''' one '''''comma''''' twenty '''''comma''''' two '''– generates integers from

1 to 19 with step of 2

'''range '''''inside parentheses''''' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the list.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten

Execute this in the '''Python''' interpreter.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for''' loop in a Python terminal window.

Start the '''Python''' '''interpreter''' by issuing the '''command''' '''python '''in a '''new terminal'''.

Type,

'''for i '''in range ''inside parentheses''''' one '''''comma '''''eleven '''''colon''''' '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python''' interpreter does not indent the code automatically.

So enter four spaces there and then type the following

'''print'' '''''inside parentheses''''' ''i '''''comma inside quotes''' ''cube is '''''comma''''' i '''''raised to''''' '''''power of''''' three'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit enter, we still see the three dots.

To get out of the block, press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! so the main thing we learnt here is -

* how to use the '''Python''' '''interpreter''' and

* the '''IPython''' interpreter to specify blocks.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython''' interpreter for ease of use.

The problem can be solved by just using the '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

for i in range(1, 51, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| for''' i''' in '''range''' ''inside parentheses '''''one''' ''comma'' '''fifty one''' ''comma''''' two''''' colon ''

print'' inside parentheses'' '''i''' and press '''Enter '''twice

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight parameters in '''range '''function and highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate element.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create blocks in python using''' for'''
# Indent the blocks of code
# Iterate over a list using '''for''' loop
# Use the '''range()''' function

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for '''loop to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2.

'''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-for/English

2017-11-15T09:35:22Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for''' loop.
# Use '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use lists.

If not, see the relevant Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
Here the loop variable iterates over a list of numbers and finds the square root of each number.
Here the loop variable takes the value of the item inside the sequence on each iteration.

For each '''item,''' the '''loop''' '''body''' is '''executed. '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''‘For’''' loop and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for''' loop. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the '''for''' loop iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36

Note that here we used two variables,

* '''numbers -''' which is a list of numbers
* '''num''' - which is the element of list under consideration in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for''' '''statement''' '''indicates''' the starting of '''loop''' '''body'''.

Every '''statement '''in '''loop''' starts''' with 4 spaces'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single statement in the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for''' loop.

And the lines after that don't fall in the scope of the '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each block is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home '''directory'''.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as,

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

We get the square root of the given numbers executed by the for loop.

This is the print statement output executed after the for loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in sqrt_num_list.py

* Type each line of the code in the '''IPython''' '''interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Type,

'''numbers '''''equal to inside square brackets''''' 4, 9, 16, 25, 36'''

'''for num in numbers '''''colon''''' '''Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the prompt changes to three dots.

And the cursor is not right after the three dots but, there are four spaces from the dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the block.

The three dots tell you that you are inside a block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop''', '''print'' '''inside parentheses inside quotes sqrt of comma '''''num '''''comma inside quotes is comma''''' num '''''raised to power of''''' 0.5'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the statements in the block.

But still the interpreter is showing three dots, this means that you are still inside the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the block press the '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the list, which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range '''built-in function in Python.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range '''''inside parentheses inside square brackets''''' start '''''comma close square brackets '''''stop '''''open square brackets comma''''' step '''''close square brackets''

For example:

'''range '''''inside parentheses''''' one '''''comma''''' twenty '''''comma''''' two '''– generates integers from

1 to 19 with step of 2

'''range '''''inside parentheses''''' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the list.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten

Execute this in the '''Python''' interpreter.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for''' loop in a Python terminal window.

Start the '''Python''' '''interpreter''' by issuing the '''command''' '''python '''in a '''new terminal'''.

Type,

'''for i '''in range ''inside parentheses''''' one '''''comma '''''eleven '''''colon''''' '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python''' interpreter does not indent the code automatically.

So enter four spaces there and then type the following

'''print'' '''''inside parentheses''''' ''i '''''comma inside quotes''' ''cube is '''''comma''''' i '''''raised to''''' '''''power of''''' three'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit enter, we still see the three dots.

To get out of the block, press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! so the main thing we learnt here is -

* how to use the '''Python''' '''interpreter''' and

* the '''IPython''' interpreter to specify blocks.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython''' interpreter for ease of use.

The problem can be solved by just using the '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

for i in range(1, 51, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| for''' i''' in '''range''' ''inside parentheses '''''one''' ''comma'' '''fifty one''' ''comma''''' two''''' colon ''

print'' inside parentheses'' '''i''' and press '''Enter '''twice

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight parameters in '''range '''function and highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate element.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create blocks in python using''' for'''
# Indent the blocks of code
# Iterate over a list using '''for''' loop
# Use the '''range()''' function

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for '''loop to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2.

'''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-for/English

2017-11-15T06:59:17Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for''' loop.
# Use '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use lists.

If not, see the relevant Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''for''' statement iterates over the members of a sequence in order, executing the block each time.

Here the loop variable takes the value of the item inside the sequence on each iteration.

For each '''item,''' the '''loop''' '''body''' is '''executed. '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''‘For’''' loop and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for''' loop. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the '''for''' loop iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, and 36

Note that here we used two variables,

* '''numbers -''' which is a list of numbers
* '''num''' - which is the element of list under consideration in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for''' '''statement''' '''indicates''' the starting of '''loop''' '''body'''.

Every '''statement '''in '''loop''' starts''' with 4 spaces'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single statement in the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for''' loop.

And the lines after that don't fall in the scope of the '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each block is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home '''directory'''.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as,

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

We get the square root of the given numbers executed by the for loop.

This is the print statement output executed after the for loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in sqrt_num_list.py

* Type each line of the code in the '''IPython''' '''interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Type,

'''numbers '''''equal to inside square brackets''''' 4, 9, 16, 25, 36'''

'''for num in numbers '''''colon''''' '''Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the prompt changes to three dots.

And the cursor is not right after the three dots but, there are four spaces from the dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the block.

The three dots tell you that you are inside a block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop''', '''print'' '''inside parentheses inside quotes sqrt of comma '''''num '''''comma inside quotes is comma''''' num '''''raised to power of''''' 0.5'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the statements in the block.

But still the interpreter is showing three dots, this means that you are still inside the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the block press the '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the list, which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range '''built-in function in Python.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range '''''inside parentheses inside square brackets''''' start '''''comma close square brackets '''''stop '''''open square brackets comma''''' step '''''close square brackets''

For example:

'''range '''''inside parentheses''''' one '''''comma''''' twenty '''''comma''''' two '''– generates integers from

1 to 19 with step of 2

'''range '''''inside parentheses''''' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the list.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten

Execute this in the '''Python''' interpreter.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for''' loop in a Python terminal window.

Start the '''Python''' '''interpreter''' by issuing the '''command''' '''python '''in a '''new terminal'''.

Type,

'''for i '''in range ''inside parentheses''''' one '''''comma '''''eleven '''''colon''''' '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python''' interpreter does not indent the code automatically.

So enter four spaces there and then type the following

'''print'' '''''inside parentheses''''' ''i '''''comma inside quotes''' ''cube is '''''comma''''' i '''''raised to''''' '''''power of''''' three'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit enter, we still see the three dots.

To get out of the block, press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! so the main thing we learnt here is -

* how to use the '''Python''' '''interpreter''' and

* the '''IPython''' interpreter to specify blocks.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython''' interpreter for ease of use.

The problem can be solved by just using the '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

for i in range(1, 51, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| for''' i''' in '''range''' ''inside parentheses '''''one''' ''comma'' '''fifty one''' ''comma''''' two''''' colon ''

print'' inside parentheses'' '''i''' and press '''Enter '''twice

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight parameters in '''range '''function and highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate element.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create blocks in python using''' for'''
# Indent the blocks of code
# Iterate over a list using '''for''' loop
# Use the '''range()''' function

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for '''loop to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2.

'''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}

Python-3.4.3/C2/Getting-started-with-for/English

2017-11-15T06:35:10Z

Trupti:

'''Title of script''': Getting started with '''for loops'''

'''Author: Trupti, Thirumalesh H S'''

'''Keywords:Python, IPython, for loop, blocks, indent, iterate, loop'''
{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| At the end of this tutorial, you will be able to,

# Use the '''for''' loop.
# Use '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To record this tutorial, I am using,

* '''Ubuntu Linux 14.04''' operating system
* '''Python 3.4.3'''
* '''IPython 5.1.0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide:

Pre-requisite

If not, see the relavant Python tutorials on http://spoken-tutorial.org

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To practice this tutorial, you should know how to use lists.

If not, see the relevant Python tutorials on this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| First let us see the syntax of '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide

Syntax: For

<nowiki>for <loop variable> in sequence:</nowiki>

<nowiki><statement 1></nowiki>

<nowiki><statement 2> </nowiki>

...
<nowiki><statement n></nowiki>

'''Highlight according to narration'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''for''' statement iterates over the members of a sequence in order, executing the block each time.

Here the loop variable takes the value of the item inside the sequence on each iteration.

For each '''item,''' the '''loop''' '''body''' is '''executed. '''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see an example of '''‘For’''' loop and how to execute it.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''ipython3'''

| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

Now, type '''ipython3''' and press '''Enter'''.

|-
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| <nowiki>[IPython console]</nowiki>

'''%pylab '''and press '''Enter.'''
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.014cm;padding-right:0.191cm;"| Let us initialise the '''pylab''' package.

Type '''%pylab '''and press''' Enter.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Open your '''text''' '''editor'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight according to narration

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us write a '''for''' loop. Type the code as shown here:

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers:'''

'''print(“sqrt of”, num, '''''“is”, num**0.5)''

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here the '''for''' loop iterates over a list of numbers and finds the square root of each number.

The numbers are: 4, 9, 16, 25, 36

Note that here we used two variables,

* '''numbers -''' which is a list of numbers
* '''num''' - which is the element of list under consideration in each cycle of the '''for loop'''.

The variable names can be any of your choice.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch back to the editor.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us switch back to the text editor.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that a '''colon''' after the '''for''' '''statement''' '''indicates''' the starting of '''loop''' '''body'''.

Every '''statement '''in '''loop''' starts''' with 4 spaces'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the line after '''for '''statement
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

In this example, it is only a single statement in the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the fifth line -

'''print("This is outside for-loop")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the line '''print("This is outside for-loop")''' is not indented.

It means that it is not a part of the''' for''' loop.

And the lines after that don't fall in the scope of the '''for''' loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight indentation
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Thus each block is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as sqrt_num_list.py
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Save the file as '''sqrt_num_list.py '''in the''' home '''directory'''.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| switch back to your terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now switch back to your terminal.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Save & run script

Highlight the output

'''%run -i sqrt_num_list.py'''

sqrt of 4 is 2.0

sqrt of 9 is 3.0

sqrt of 16 is 4.0

sqrt of 25 is 5.0

sqrt of 36 is 6.0

This is outside for-loop

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Run the script using the '''run''' command as,

'''''percent'' run ''minus'' i filename '''and press '''Enter.'''

We get the square root of the given numbers executed by the for loop.

This is the print statement output executed after the for loop.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 1

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
* Use the same example we used in sqrt_num_list.py

* Type each line of the code in the '''IPython''' '''interpreter prompt. '''

* Skip the line: '''print("This is outside for-loop")'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''<nowiki>numbers = [4, 9, 16, 25, 36]</nowiki>'''

'''for num in numbers: '''Press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal.

Type,

'''numbers '''''equal to inside square brackets''''' 4, 9, 16, 25, 36'''

'''for num in numbers '''''colon''''' '''Press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight the dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| You will notice that, the prompt changes to three dots.

And the cursor is not right after the three dots but, there are four spaces from the dots.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight the three dots
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please note that '''IPython''' automatically indents the block.

The three dots tell you that you are inside a block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

'''print(“sqrt of”, num, ''''''“is”, num**0.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now type the rest of the '''for loop''', '''print'' '''inside parentheses inside quotes sqrt of comma '''''num '''''comma inside quotes is comma''''' num '''''raised to power of''''' 0.5'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now we have finished the statements in the block.

But still the interpreter is showing three dots, this means that you are still inside the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

press '''Enter''' twice
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To exit from the block press the '''Enter''' key twice without entering anything else.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| It printed the square root of each number in the list, which was executed in the '''for loop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Next we will see about '''range '''built-in function in Python.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

'''range()''' function

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''range()''' function generates a '''list''' of '''integers.'''

The syntax is: '''range '''''inside parentheses inside square brackets''''' start '''''comma close square brackets '''''stop '''''open square brackets comma''''' step '''''close square brackets''

For example:

'''range '''''inside parentheses''''' one '''''comma''''' twenty '''''comma''''' two '''– generates integers from

1 to 19 with step of 2

'''range '''''inside parentheses''''' twenty '''– generates integers from 0 to 19

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>

Highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the ending number that you specify will not be included in the list.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 2

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Find out the cube of all the numbers from one to ten

Execute this in the '''Python''' interpreter.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

'''python'''

'''for i in range(1, 11):'''

press '''Enter'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us now try to run the '''for''' loop in a Python terminal window.

Start the '''Python''' '''interpreter''' by issuing the '''command''' '''python '''in a '''new terminal'''.

Type,

'''for i '''in range ''inside parentheses''''' one '''''comma '''''eleven '''''colon''''' '''press '''Enter'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

Highlight the cursor
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will see that this time it shows three dots, but the cursor is close to the dots.

So we have to indent the block.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

'''print(i, "cube is", i**3)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''Python''' interpreter does not indent the code automatically.

So enter four spaces there and then type the following

'''print'' '''''inside parentheses''''' ''i '''''comma inside quotes''' ''cube is '''''comma''''' i '''''raised to''''' '''''power of''''' three'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>

press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now when we hit enter, we still see the three dots.

To get out of the block, press '''Enter''' once again.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Python Terminal]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Okay! so the main thing we learnt here is -

* how to use the '''Python''' '''interpreter''' and

* the '''IPython''' interpreter to specify blocks.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Exercise 3

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Print all the odd numbers from 1 to 50.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us do it in our '''IPython''' interpreter for ease of use.

The problem can be solved by just using the '''range()''' function.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

for i in range(1, 51, 2):

print(i)

press '''Enter '''twice

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| for''' i''' in '''range''' ''inside parentheses '''''one''' ''comma'' '''fifty one''' ''comma''''' two''''' colon ''

print'' inside parentheses'' '''i''' and press '''Enter '''twice

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki>

Highlight parameters in '''range '''function and highlight output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The first '''parameter''' is the starting number of the sequence.

The second '''parameter''' is the end of the '''range'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight third parameter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

Here we gave '''two''' which means we are skipping every alternate element.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This brings us to the end of the tutorial.

In this tutorial, we learnt to,

# Create blocks in python using''' for'''
# Indent the blocks of code
# Iterate over a list using '''for''' loop
# Use the '''range()''' function

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Assignment

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

1. Indentation is not mandatory in '''Python'''

* True
* False

2. Write a '''for '''loop to print the product of all natural numbers from 1 to 20.

3. What will be the output of:

'''range(1, 5)'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Solution of self assessment questions on slide

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

2.

'''y '''''equal to''''' one'''

'''for x in range '''''inside parentheses''''' one '''''comma''''' twenty one''''' colon''''' '''

'''y''''' into equal to''''' x'''

'''print '''''inside parentheses '''''y'''

3. '''range(1, 5)'''<nowiki> will produce a list of integers from 1 to 4 [1,2,3,4]</nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Fossee Forum
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Textbook Companion
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Slide

Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Previous slide
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is _________ from IIT Bombay (or FOSSEE, if you wish) signing off.

Thank you.

|}