Pratik kamble: Created page with "{| border=1 | '''Time''' |'''Narration''' |- | 00:01 | Hello Friends. Welcome to the tutorial on "'''Getting started with lists'''". |- | 00:07 | At the end of this tutoria..."

2019-06-11T06:52:54Z

Created page with "{| border=1 | '''Time''' |'''Narration''' |- | 00:01 | Hello Friends. Welcome to the tutorial on "'''Getting started with lists'''". |- | 00:07 | At the end of this tutoria..."

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{| border=1
| '''Time'''
|'''Narration'''

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

|-
| 00:07
| At the end of this tutorial, you will be able to,

Create '''lists '''

Access '''list elements '''

'''Append elements''' to '''lists''' and

'''Delete elements''' from '''lists '''

|-
| 00:21
|To record this tutorial, I am using

'''Ubuntu Linux 14.04''' operating system

'''Python 3.4.3'''

'''IPython 5.1.0'''

|-
| 00:35
|To practise this tutorial, you should know how to

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

If not, see the relevant '''Python '''tutorials on this website.

|-
|00:48
|What is a List?

A List can store a sequence of elements.

All elements need not be of the same data types

|-
| 00:59
| Let us open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously

|-
| 01:06
| Now, type '''ipython3''' and press '''Enter'''. We are now in the '''ipython''' prompt.
Let us clear the '''terminal''' by pressing '''Ctrl + L''' for better view.

|-
| 01:20
| Let us define a '''list''' with a variable name '''mylist'''

|-
| 01:25
|Type

'''mylist '''''equal to'' ''inside square brackets inside quotes''''' spam '''''comma''''' '''''inside quotes '''''eggs''' ''comma''' ''hundred '''''comma''''' one point two three four '''and''' '''press '''Enter'''.

|-
| 01:45
|In '''Python, strings''' are always placed inside single or double quotes.

|-
| 01:52
| Now enter''' type '''within brackets '''mylist '''and'' ''press '''Enter'''.

|-
| 02:01
| Here '''type''' is a '''function''' which will return the '''datatype''' of the variable.

'''mylist''' is a '''list datatype'''.

|-
| 02:10
| As we can see, '''lists''' can contain '''elements''' of different '''datatypes'''

In '''mylist''', '''spam''' and '''eggs''' are '''strings''', whereas '''hundred''' and''' one point two three four''' are '''integer''' and '''float''' respectively.

|-
| 02:27
| In the code typed earlier, the name '''mylist''' is a variable.

|-
| 02:32
|In '''Python''', a variable must either start with an alphabet or an '''underscore'''.

|-
| 02:39
|They cannot start with numbers and cannot be the same as '''Python keywords.'''

|-
| 02:45
| You will learn about '''keywords''' as we proceed.

|-
| 02:49
|Few examples of keywords are '''“for, if, else, elif, while, in, def, or, and”.'''

|-
| 03:00
|A variable name cannot have spaces or punctuation characters or any arithmetic characters.

|-
| 03:07
| These are some of the valid and invalid variable names.

|-
| 03:14
| Getting back to our '''lists''', the '''list''' could be created as '''num ''underscore ''list is ''equal to''' inside square brackets ''''''''one''' ''comma '''''two'''''' and press''' Enter'''

or

|-
| 03:32
|'''x '''''equal to inside square brackets inside quotes '''''a''''' comma inside quotes '''''b''''' ''and press''' Enter'''

Any valid variable name could be used.

|-
| 03:50
| Let us now create an '''empty list '''with no elements.

|-
| 03:55
|Type '''myemptylist '''''is equal to open and close square brackets ''and press '''Enter'''.
This is an '''empty list''' without any '''element'''

|-
| 04:08
| We can access an '''element''' of a '''list''' using its corresponding '''index''' or '''position'''.

|-
| 04:15
|'''Index value''' of the '''elements''' starts from 0, 1, 2 and so on.

|-
| 04:22
|'''Negative indices''' are used to access '''elements''' from the end. Which starts from -1, -2, and so on

|-
| 04:33
|The syntax to get a specific '''list element''' is

'''variable '''''inside square brackets '''''elements index value'''

|-
| 04:44
| Switch to the '''terminal'''.

|-
| 04:47
| Type '''mylist'' '''inside square brackets''' ''zero '''and press '''Enter'''.

As we can see''' mylist[0]''' gives the first '''element spam'''

|-
| 05:00
|Type '''mylist '''''inside square brackets''' ''one '''and press '''Enter'''.

'''mylist[1] '''gives the second '''element'''.

|-
| 05:11
| Pause the video. Try this exercise and then resume the video.

What happens when you type '''mylist[-1]'''.

|-
| 05:21
| Switch to the '''terminal''' for solution

|-
| 05:25
|Type '''mylist '''''inside square brackets '''''minus one''''' ''and''' '''press '''Enter'''.

As you can see you get the last '''element''' which is '''one point two three four. '''

|-
|05:39
| We can also create a '''list''' inside a '''list.'''

|-
| 05:43
|This property makes '''lists heterogeneous data structures'''. This is the syntax for '''list''' inside a '''list'''.

|-
| 05:53
| Let us include a '''list''' within a '''list''' for the variable '''doublelist'''.

|-
| 05:59
|Type the code as shown here: Here '''b c d''' is a '''list''' in '''list''' which is represented within square brackets inside a '''list'''.

|-
| 06:11
| Now let us fetch some element from '''doublelist'''.

Type:''' doublelist '''''inside square brackets '''''one''' and press '''Enter'''

|-
| 06:23
|We can see the output as '''b c d '''within square brackets. This is because the '''index value one''' contains the '''list''' inside a '''list''' as its '''element'''.

|-
| 06:37
| Now let us try to access a specific '''element''', say''' b''' from the '''list''' inside a '''list'''.

|-
| 06:45
|For this type: '''doublelist''''' inside square brackets ''one ''inside square brackets '''''zero '''and press '''Enter'''.

|-
| 06:57
|Here the 1st '''parameter''' represents the '''index''' of the '''list''' in the main '''list'''.

|-
| 07:04
|The second '''parameter''' represents the '''index value''' of '''b''' in the '''list''' inside the '''list'''.

|-
| 07:12
| Pause the video. Try this exercise and then resume the video.

'''doublelist=[‘a’, [‘b’,’c’,’d’], 'and', 5, 6, 7, 8] '''

|-
| 07:18
| What is the command to get the '''element 'and'''' in the '''list ''doublelist'''''?

|-
| 07:24
| How would you get ''''and'''' using negative '''indices'''?

|-
| 07:28
| How would you get '''element 'd'''' from the '''list ''doublelist'''''?

|-
| 07:33
| The solution is on your screen.

|-
| 07:38
| We can use '''len function''' to check the number of '''elements/length of '''in the '''list'''.

The syntax is: '''len''' ''inside parentheses '''''variable'''

|-
| 07:49
| Let us find the number of elements in '''mylist''' which we created earlier.

|-
| 07:55
|Switch to the''' terminal '''and clear the screen. Recall '''mylist''' by pressing up arrow key and press''' Enter.'''

|-
| 08:05
|Type '''len '''''inside parentheses '''''mylist '''and press '''Enter.''' We get the length of '''mylist''' as '''four'''.

|-
| 08:16
| We can append '''elements''' to the '''list''' using the '''append function'''.

|-
| 08:21
|This '''function''' will add the '''element''' to the end of the '''list'''.

|-
| 08:26
|The syntax is: '''variable''' ''dot'' '''append''' within ''parentheses '''element''' to be added.''

|-
| 08:35
| Switch to the '''terminal'''

Now type

'''mylist''''' dot'' '''append''' ''inside parentheses within quotes''' ''sharp''' and''' '''press '''Enter'''.

|-
| 08:49
|Type''' mylist '''''dot'' '''append''' ''inside parentheses''' ''six'' '''''and''' '''press '''Enter.'''

|-
| 08:57
| Let us check the '''updated mylist.''' Type''' mylist '''and press '''Enter ''' We can see '''mylist''' is '''appended''' with '''sharp''' and '''six''' at the end.

|-
| 09:10
|We can also remove '''elements''' from '''lists'''.

There are two ways of doing it. One is by using the '''index '''with''' del keyword'''.

Syntax is '''del '''variable ''inside square brackets '''element’s ''index value'''.

|-
| 09:29
|The other way is removing '''element''' by the value using '''remove function'''

Syntax is '''variable '''''dot '''''remove '''''inside parentheses '''''element to be removed'''

|-
| 09:43
| Switch to the''' terminal.'''

Type '''mylist''' and press''' Enter '''to see the updated '''list'''.

Type '''del '''''space '''''mylist '''''inside square brackets''''' one '''and press '''Enter.'''

|-
| 10:01
|The '''keyword del''' deletes the '''element''' at '''index''' one, i.e the second '''element''' of the '''list, eggs'''.

|-
| 10:11
| Again type '''mylist''' and press''' Enter'''. We can see that the '''element eggs''' has been deleted from the '''list'''.

|-
| 10:22
| Let us delete the '''element hundred''' from '''mylist list'''.

|-
|10:27
|For this we can use the '''function remove'''. Type '''mylist''''' dot '''''remove '''within parentheses''' hundred '''and press '''Enter.'''

Let us check the '''updated mylist.'''

|-
| 10:44
| What if the '''elements''' are repeated?

|-
|10:47
|To check that, let’s do a small experiment.Type '''mylist''''' dot '''''append '''within parentheses within quotes '''spam '''and press''' Enter'''

|-
| 11:01
|Type '''mylist '''and press''' Enter''' Here is the '''updated mylist.'''

|-
| 11:08
|It contains the '''element spam''' twice. One is at the start and the next is at the end of the '''list'''.

|-
| 11:17
| Now remove the '''element spam''' by typing: '''mylist '''''dot '''''remove '''''inside parentheses inside quotes'' '''spam '''and press '''Enter.'''

Let us check '''updated mylist.'''

|-
| 11:35
| We can see that only the first occurrence of ''''spam'''' has been removed.

|-
| 11:41
|The '''function remove''' removes the first occurrence of the '''element''' in the sequence.

Remember, the '''del keyword''' removes the '''element''' by '''index value'''. '''remove function''' removes on the basis of '''element''' being passed on.

|-
| 11:57
| Using '''remove function''', we can also remove an '''element''' with its '''index value'''.

|-
| 12:03
| Let us try this with an example. Type''' k '''''is equal to inside square brackets '''''one''''' comma '''''two''''' comma '''''one''''' comma '''''three '''and press''' Enter'''

|-
| 12:17
|Then type '''k '''''dot '''remove''' inside parentheses''''' k inside square brackets two '''and press''' Enter''' Type''' k '''and press '''Enter ''' We can see the output as'''[2,1,3].'''

|-
| 12:36
|Since it '''deletes''' the first occurrence of what is returned by '''k '''''inside square brackets''''' two''' which is''' one'''.

|-
| 12:45
| Pause the video. Try this exercise and then resume the video.

1. Delete the fourth '''element''' from the '''list doublelist'''.

2. Remove ''''and'''' from the '''list doublelist'''.

|-
| 12:58
| The solution is on your screen.

|-
| 13:04
|This brings us to the end of this tutorial.

In this tutorial, we have learnt to create:

'''List''' with '''elements'''

'''Empty list'''

'''List''' within a '''list'''

|-
| 13:18
|We also learnt to,

Find out the '''list''' length using '''len function'''.

Access '''elements''' using their '''index''' numbers.

|-
| 13:28
|Append '''elements''' to '''list''' using the '''function append'''.

Delete '''element''' from list using the '''del''' and '''remove function'''

|-
| 13:37
|Here are some self assessment questions for you to solve

How do you create an '''empty list'''?

Can you have a '''list''' inside a '''list'''?

How would you access the last '''element''' of a '''list''' without finding its length?

|-
| 13:54
| And the answers,

1. We create an '''empty list''' just by leaving the space inside the square brackets empty. '''myemptylist''' equal to open and close square brackets.

|-
| 14:07
|2. Yes, '''list''' can contain all the other '''data types''', including '''list'''.

3. Using negative '''indices''', we can access the last '''element''' from the '''list'''.

|-
| 14:19
| Please post your timed queries in this forum.

|-
| 14:23
| Please post your general queries on Python in this forum.

|-
| 14:28
| FOSSEE team coordinates the TBC project.

|-
| 14:33
| Spoken-tutorial is funded by NMEICT, MHRD, Govt. of India. For more details, visit this website.

|-
| 14:44
| This is Trupti Kini from IIT Bombay signing off. Thank you.

|}

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

Pratik kamble: Created page with "{| border=1 | '''Time''' |'''Narration''' |- | 00:01 | Hello Friends. Welcome to the tutorial on "'''Getting started with lists'''". |- | 00:07 | At the end of this tutoria..."