PoojaMoolya: Created page with " {| border=1 | '''Time''' | '''Narration''' |- | 00:01 | Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''"..."

2019-05-30T10:55:45Z

Created page with " {| border=1 | <center>'''Time'''</center> | <center>'''Narration'''</center> |- | 00:01 | Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''"..."

New page

{| border=1
| <center>'''Time'''</center>
| <center>'''Narration'''</center>

|-
| 00:01
| Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''".

|-
| 00:08
| At the end of this tutorial, you will be able to,

Use the '''for loop'''.

Use '''range() function'''.

|-
| 00:17
| To record this tutorial, I am using,

'''Ubuntu Linux 14.04''' operating system

|-
| 00:25
| '''Python 3.4.3''' and '''IPython 5.1.0'''

|-
| 00:32
| To practice this tutorial, you should know how to use '''lists'''.

|-
| 00:37
| If not, see the relevant '''Python''' tutorials on this website.

|-
| 00:42
| First let us see the syntax of '''for loop'''.

|-
| 00:46
|'''for statement''' iterates over the members of a sequence in order, executing the '''block''' each time.

|-
| 00:54
| Here the '''loop variable''' takes the value of the '''item''' inside the sequence on each iteration.

|-
| 01:01
| For each '''item,''' the '''loop body''' is executed.

|-
| 01:05
| We will see an example of '''for loop''' and how to execute it.

|-
| 01:10
| Let us first open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously.

|-
| 01:17
| Now, type '''ipython3''' and press '''Enter'''.

|-
| 01:22
| Let us initialise the '''pylab package'''.

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

|-
| 01:30
| Open your '''text editor'''.

|-
| 01:33
| Let us write a '''for loop'''. Type the code as shown here:

|-
| 01:39
| Here the loop variable iterates over a list of numbers and finds the square root of each number.

|-
| 01:46
| The numbers are: 4, 9, 16, 25, and 36.

|-
| 01:52
| Note that here we used two variables, '''numbers ''' which is a '''list''' of numbers

|-
| 02:00
| '''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.

|-
| 02:11
| Note that a '''colon''' after the '''for statement''' indicates the starting of '''loop body'''.

|-
| 02:18
| Every '''statement '''in '''loop''' starts with 4 spaces.

|-
| 02:24
| It means that, the line is a '''block''' of '''code''' in '''for loop'''.

|-
| 02:29
|In this example, it is only a single '''statement''' in the '''block'''.

|-
| 02:35
| 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'''.

|-
| 02:46
| And the lines after that don't fall in the scope of the '''for loop'''.

|-
| 02:51
| Thus each '''block''' is separated by the indentation level.

This marks the importance of '''white-spaces''' in '''Python'''.

|-
| 03:01
| Save the file as '''sqrt_num_list.py '''in the''' home directory'''.

|-
| 03:13
| Now switch back to your '''terminal'''.

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

|-
| 03:19
| Run the script using the '''run''' command as '''''percent'' run ''minus'' i filename '''and press '''Enter.'''

|-
| 03:31
| We get the square root of the given numbers executed by the '''for loop'''.

|-
| 03:37
| This is the '''print statement''' output executed after the '''for loop'''.

|-
| 03:42
| Use the same example we used in '''sqrt_num_list.py'''

|-
| 03:48
| Type each line of the code in the '''IPython interpreter prompt. '''

|-
| 03:53
| Skip the line: '''print("This is outside for-loop")'''

|-
| 03:58
| Switch to the '''terminal'''.

|-
| 04:01
| Type,'''numbers ''equal to inside square brackets'' 4, 9, 16, 25, 36''' and press '''Enter'''

|-
| 04:20
| '''for num in numbers '''''colon'' Press '''Enter'''

|-
| 04:27
| 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.

|-
| 04:40
| Please note that '''IPython''' automatically indents the '''block'''.

The three dots tell you that you are inside a '''block'''.

|-
| 04:50
| 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'''

|-
| 05:19
| Now we have finished the '''statements''' in the '''block'''.

But still the '''interpreter''' is showing three dots.

|-
| 05:26
| This means that you are still inside the '''block'''.

|-
| 05:30
| To exit from the '''block''', press '''Enter''' key twice without entering anything else.

|-
| 05:37
| It printed the square root of each number in the '''list''', which was executed in the '''for loop.'''

|-
| 05:44
| Next we will see about '''range built-in function''' in '''Python'''.

|-
| 05:48
| '''range()''' function generates a '''list''' of '''integers.'''

|-
| 05:52
| The syntax is: '''range start ''comma'' stop ''comma'' step'''

|-
| 05:59
| For example: '''range ''inside parentheses'' one ''comma'' twenty ''comma'' two ''' generates integers from 1 to 19 with step of 2

|-
| 06:11
| '''range ''inside parentheses'' twenty ''' generates integers from 0 to 19

|-
| 06:18
| Note that the ending number that you specify will not be included in the '''list'''.

|-
| 06:25
| Find out the cube of all the numbers from one to ten.

Execute this in the '''Python interpreter'''.

|-
| 06:34
| Let us now try to run the '''for loop''' in a '''Python terminal''' window.

|-
| 06:40
| Open a new '''terminal''' by pressing '''Ctrl+Alt+T''' keys simultaneously.

|-
| 06:46
|Start the '''Python interpreter''' by issuing the '''command python '''in the new '''terminal''' and press '''Enter'''.

|-
| 06:54
| Type, '''for i '''in range '''''inside parentheses'' one ''comma ''eleven ''colon'' and '''press '''Enter'''

|-
| 07:06
| 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'''.

|-
| 07:17
| The '''Python interpreter''' does not indent the code automatically.

So enter four '''spaces''' and then type the following.

|-
| 07:27
| '''print ''inside parentheses'' i ''comma inside quotes ''cube is ''comma'' i ''raised to power of'' three''' press '''Enter'''.

|-
| 07:44
| Now when we hit '''Enter''', we still see the three dots.

To get out of the '''block''', press '''Enter''' once again.

|-
| 07:53
| Okay! So the main thing we learnt here is - how to use the '''Python interpreter''' and

the '''IPython interpreter''' to specify '''blocks'''.

|-
| 08:03
| Print all the odd numbers from 1 to 50.

|-
| 08:07
| Let us do it in our '''IPython interpreter''' for ease of use.

|-
| 08:12
| The problem can be solved by just using the '''range() function'''.

|-
| 08:17
| Let us clear the '''terminal'''.

|-
| 08:20
| for''' i ''in range inside parentheses'' one ''comma'' fifty ''comma'' two ''colon '''

press '''Enter '''

'''print'' inside parentheses'' i''' press '''Enter '''twice.

|-
| 08:40
| The first '''parameter''' is the starting number of the sequence.

|-
| 08:45
| The second '''parameter''' is the end of the '''range'''.

|-
| 08:49
| Note that the '''sequence''' does not include the ending number.

The third '''parameter''' is for stepping through the '''sequence'''.

|-
| 08:59
| Here we gave '''two''' which means we are skipping every alternate '''element'''.

|-
| 09:05
| This brings us to the end of the tutorial.

In this tutorial, we learnt to, Create '''blocks''' in '''python''' using''' for'''

|-
| 09:15
| Indent the '''blocks''' of code

|-
| 09:17
| Iterate over a list using '''for loop''' and Use the '''range() function'''

|-
| 09:23
| Here are some self assessment questions for you to solve

Indentation is not mandatory in '''Python'''

True or False

|-
| 09:32
| Write a '''for loop''' to print the product of all natural numbers from 1 to 20.

What will be the output of: '''range(1, 5)'''

|-
| 09:43
| And the answers,

1. False, '''Indentation''' is essential in '''python'''.

|-
| 09:51
| 2. '''y '''''equal to''''' one'''

'''for x in range ''' one '''''comma''''' twenty one'''''

|-
| 09:58
| '''y''''' into equal to''''' x'''

'''print y'''

|-
| 10:03
| 3. '''range(1, 5)''' will produce a list of integers from 1 to 4 i.e. [1,2,3,4]

|-
| 10:14
| Please post your timed queries in this forum.

|-
| 10:18
| Please post your general queries on Python in this forum.

|-
| 10:23
| FOSSEE team coordinates the TBC project.

|-
| 10:27
| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

|-
| 10:37
| This is Trupti Kini from IIT Bombay signing off.

Thank you.

|}

Python-3.4.3/C3/Getting-started-with-for/English-timed - Revision history

PoojaMoolya: Created page with " {| border=1 | '''Time''' | '''Narration''' |- | 00:01 | Hello Friends. Welcome to the tutorial on "Getting started with '''for loops'''"..."