View source for Python-3.4.3/C3/Getting-started-with-strings/English-timed

{| border=1
| '''Tiime'''
| '''Narration'''

|-
| 00:01
| Hello Friends. Welcome to the tutorial on "'''Getting Started with Strings'''". 

|-
| 00:07
|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. 

|-
| 00:24
|To record this tutorial, I am using 

'''Ubuntu Linux 16.04''' operating system

'''Python 3.4.3''' and '''IPython 5.1.0'''

|-
| 00:39
|To practise this tutorial, you should know how to 

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

|-
| 00:48
| If not, see the pre-requisite '''Python '''tutorials on this website.

|-
| 00:54
| What are '''strings'''? 
In '''Python,''' any character within a '''single/ double/ triple quotes '''is''' '''a''' string.'''

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| 01:03
| For example: 
Single, double, and triple '''quotes''' can be used to denote a '''string '''as shown here.

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| 01:13
| '''Strings''' in triple '''quotes''' can be written in multiple '''lines'''.

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| 01:19
| We can also define empty '''strings'''. '''String''' is a collection of characters which cannot be modified after it is created.

|-
| 01:30
| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously. Type '''ipython3''' and press '''Enter'''. 

|-
|01:42
| Let us initialise the '''pylab''' package.Type '''%pylab '''and press''' Enter.'''

|-
| 01:51
| Let us clear the terminal.

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

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| 01:58
| Type '''a '''''is equal to inside any quotes'' '''Hello''' ''comma'' '''World''' '''exclamation mark '''and

Press '''Enter'''

|-
| 02:09
| Now let us learn string concatenation. Let us assign strings to variables.

|-
|02:16
| Type 

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

Press '''Enter'''

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

Press '''Enter'''

|-
| 02:32
| 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'''

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| 02:52
|'''print''' ''inside parentheses'' '''z'''

Press '''Enter'''

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

|-
| 03:04
| The '''addition''' '''operation''' performs the '''concatenation''' of two '''strings'''. 

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| 03:09
| Here we can see the output of string concatenation.

|-
| 03:14
| Let us clear the '''terminal'''.

What if we multiply a string with an integer?

Let us find out!

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| 03:23
|Recall''' x''' string.

Press '''Enter'''

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

Press '''Enter'''

|-
| 03:33
| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''. 

|-
| 03:39
| Pause the video. Try this exercise and then resume the video.

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

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| 03:51
| 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'''

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| 04:14
| '''print''' ''inside parentheses '' '''s''' Press '''Enter'''

|-
| 04:20
| Let's now look at '''accessing''' individual '''elements''' of '''strings'''.  We can access individual '''elements''' in the '''string''' using the '''subscripts.''' 

|-
| 04:30
| 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'''. 

|-
| 04:47
| The '''indexing''' starts from 0 and goes up to '''(n-1)'''.

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

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| 04:57
| We can '''access''' the '''strings''' from the end using '''negative indices.'''

|-
| 05:02
| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark'''

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| 05:11
| '''a '''''inside square brackets '''''minus two''' gives us the second '''element''' from the end of the '''string''' i.e. '''d'''

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| 05:21
| 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

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| 05:33
| Switch to the '''terminal'''.

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| 05:35
| Let us clear the '''terminal'''.

Type

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

|-
| 05:46
| '''s '''''inside square brackets '''minus'' five''' gives '''W '''

Similarly we will get '''e ''' for s[-10].

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| 05:59
| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. ''' Since the string given to us is only 11 '''characters''' long. 

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| 06:12
| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason.

|-
| 06:20
| Let us attempt to change one of the '''characters''' in a '''string'''.

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

Recall '''x'''

Press '''Enter'''

|-
| 06:31
| Let us manipulate '''x.'''

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

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| 06:44
| Why do we get an error?

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

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| 06:52
| Now we are trying to assign another value '''‘B’''' to '''x[0]'''. Recall, strings cannot be modified after it is created.

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| 07:02
| We can split and join the strings by using the functions : '''split()''' and''' join()'''

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| 07:08
| To join a string, the syntax is '''str ''dot join''' inside parentheses'' '''sequence'''

|-
| 07:17
| Switch to the '''terminal'''.

|-
| 07:19
| Let us clear the '''terminal''' 

|-
| 07:22
| Type '''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter'''  '''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter'''

|-
| 07:41
| '''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter''

|-
| 07:49
| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c''' It has joined '''a, b, c''' with '''hyphen'''.

|-
| 07:57
| To split a string, syntax is '''str dot split '''''open and close parentheses ''

|-
| 08:05
| Switch to the '''terminal'''

Type as shown press '''Enter''' '''print str dot split''' ''open and close parentheses'' press '''Enter'''

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| 08:19
| We get the output like this. It has split the strings at '''spaces'''.

|-
| 08:25
| This brings us to the end of this tutorial. 

|-
| 08:28
|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. 

|-
| 08:42
| Here are some self assessment questions for you to solve 

|-
| 08:46
| 1. Write code to assign the string ’ is called the apostrophe, to variable s 

2. How will you change '''s''' '''is equal to hello''' to '''s''' '''is equal to capital H Hello'''.

|-
| 09:01
| 3. The variables '''s''' and '''t''' are strings and '''r''' is integer.

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| 09:07
| They are assigned with the values as shown below, What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''? 

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| 09:17
|And the answers, 

The given string can be assigned in this manner 

Strings cannot be manipulated after it is assigned a value

|-
| 09:29
|  The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld '''

|-
| 09:41
| Please post your timed queries in this forum.

|-
| 09:45
| Please post your general queries on Python in this forum.

|-
| 09:50
| FOSSEE team coordinates the TBC project.

|-
| 09:54
| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India. For more details, visit this website.

|-
|10:04
| This is Trupti Kini from IIT Bombay signing off. Thank you.

|}