Difference between revisions of "Python-3.4.3/C2/Getting-started-with-Lists/English"

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|-
 
|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Show Slide  
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Show Title 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:0.079cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting started with lists'''".  
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Hello Friends. Welcome to the tutorial on "'''Getting started with lists'''".  
  
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'''ipython3'''
 
'''ipython3'''
  
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0cm;padding-right:0.191cm;"| let us open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously
+
| style="background-color:#ffffff;border:1pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0cm;padding-right:0.191cm;"| Let us open the '''Terminal '''by pressing '''Ctrl+Alt+T '''keys simultaneously
  
 
Now, type '''ipython3''' and press '''Enter'''.  
 
Now, type '''ipython3''' and press '''Enter'''.  
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We are now in the '''ipython''' prompt.
 
We are now in the '''ipython''' prompt.
  
Let us clear the terminal by pressing Ctrl + L for better view.
+
Let us clear the '''terminal''' by pressing '''Ctrl + L''' for better view.
  
 
|-
 
|-
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'''mylist '''''equal to'' ''inside square brackets inside quotes''''' spam '''''comma''''' '''''inside quotes '''''eggs''' ''comma''' ''hundred '''''comma''''' one point two three four '''and''' '''press '''Enter'''.  
 
'''mylist '''''equal to'' ''inside square brackets inside quotes''''' spam '''''comma''''' '''''inside quotes '''''eggs''' ''comma''' ''hundred '''''comma''''' one point two three four '''and''' '''press '''Enter'''.  
  
In Python, strings are always placed inside single or double quotes.  
+
In '''Python, strings''' are always placed inside single or double quotes.  
  
 
|-
 
|-
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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Now enter''' type '''within brackets '''mylist '''and'' ''press '''Enter'''.  
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Now enter''' type '''within brackets '''mylist '''and'' ''press '''Enter'''.  
  
Here type is a function which will return the datatype of the variable.
+
Here '''type''' is a '''function''' which will return the '''datatype''' of the variable.
  
'''mylist''' is a list datatype.  
+
'''mylist''' is a '''list datatype'''.  
  
 
|-
 
|-
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;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:0.079cm;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:0.079cm;padding-right:0.191cm;"| As we can see, lists can contain elements of different data types
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| 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.
+
In '''mylist''',  
 +
*'''spam''' and '''eggs''' are '''strings''',  
 +
*whereas '''hundred''' and''' one point two three four''' are '''integer''' and '''float''' respectively.  
  
 
|-
 
|-
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* variable must either start with an alphabet or an underscore.  
 
* variable must either start with an alphabet or an underscore.  
  
* They cannot start with numbers and cannot be the same as Python keywords.
+
* They cannot start with numbers and cannot be the same as '''Python keywords.'''
  
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| In the code typed earlier, the name '''mylist''' is a variable.
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| In the code typed earlier, the name '''mylist''' is a variable.
  
In Python, a variable must either start with an alphabet or an underscore.  
+
In '''Python''', a variable must either start with an alphabet or an '''underscore'''.  
  
They cannot start with numbers and cannot be the same as Python keywords.  
+
They cannot start with numbers and cannot be the same as '''Python keywords.'''
  
 
|-
 
|-
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* A variable name cannot have spaces or punctuation characters or any arithmetic characters.
 
* A variable name cannot have spaces or punctuation characters or any arithmetic characters.
  
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| You will learn about keywords as we proceed.
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| You will learn about '''keywords''' as we proceed.
 +
 
 +
Few examples of keywords are '''“for, if, else, elif, while, in, def, or, and”.'''
  
Few examples of keywords are “for, if, else, elif, while, in, def, or, and”.
 
  
 
A variable name cannot have spaces or punctuation characters or any arithmetic characters.
 
A variable name cannot have spaces or punctuation characters or any arithmetic characters.
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* for, in, elif
 
* for, in, elif
  
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| These are some of the valid and invalid variable names:
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| These are some of the valid and invalid variable names.
  
 
|-
 
|-
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Highlight '''<nowiki>mylist = ['spam', 'eggs', 100, 1.234] </nowiki>'''
 
Highlight '''<nowiki>mylist = ['spam', 'eggs', 100, 1.234] </nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Getting back to our lists, the list could be created as  
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| 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'''
+
'''num ''underscore ''list is ''equal to''' inside square brackets ''''''''one''' ''comma '''''two'''''' and press''' Enter'''
  
 
or
 
or
  
'''x '''''equal to inside square brackets inside quotes ''a'' comma inside quotes '''''b''''' ''and press''' Enter'''
+
'''x '''''equal to inside square brackets inside quotes '''''a''''' comma inside quotes '''''b''''' ''and press''' Enter'''
  
 
Any valid variable name could be used.
 
Any valid variable name could be used.
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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Let us now create an '''empty list '''with no elements.  
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Let us now create an '''empty list '''with no elements.  
  
Type '''myemptylist '''''is equal to open and close square brackets ''and'' ''press '''Enter'''.  
+
Type '''myemptylist '''''is equal to open and close square brackets ''and press '''Enter'''.  
  
 
This is an '''empty list''' without any '''element'''
 
This is an '''empty list''' without any '''element'''
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list index
 
list index
  
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| We can access an element of a list using its corresponding index or position.  
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| We can access an '''element''' of a '''list''' using its corresponding '''index''' or '''position'''.  
  
Index value of the elements starts from 0, 1, 2 and so on.
+
'''Index value''' of the '''elements''' starts from 0, 1, 2 and so on.
  
 
'''Negative indices''' are used to access '''elements''' from the end.
 
'''Negative indices''' are used to access '''elements''' from the end.
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Which starts from -1, -2, and so on
 
Which starts from -1, -2, and so on
  
The syntax to get a specific list element is
+
The syntax to get a specific '''list element''' is
  
'''variable '''''inside square brackets element’s '''''index value'''
+
'''variable '''''inside square brackets '''''elements index value'''
  
 
|-
 
|-
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"|  
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"|  
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Switch to the terminal
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Switch to the '''terminal'''.
  
 
|-
 
|-
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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Type '''mylist'' '''inside square brackets''' ''zero '''and press '''Enter'''.
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Type '''mylist'' '''inside square brackets''' ''zero '''and press '''Enter'''.
  
As we can see'''<nowiki> mylist[0]</nowiki>''' gives the first element''' spam'''
+
As we can see'''<nowiki> mylist[0]</nowiki>''' gives the first '''element spam'''
  
 
Type '''mylist '''''inside square brackets''' ''one '''and press '''Enter'''.
 
Type '''mylist '''''inside square brackets''' ''one '''and press '''Enter'''.
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This property makes '''lists heterogeneous data structures'''.  
 
This property makes '''lists heterogeneous data structures'''.  
  
This is the syntax for list inside a list.
+
This is the syntax for '''list''' inside a '''list'''.
  
 
|-
 
|-
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Type the code as shown here:
 
Type the code as shown here:
  
Here '''b c d''' is a list in list which is represented within square brackets inside a list
+
Here '''b c d''' is a '''list''' in '''list''' which is represented within square brackets inside a '''list'''.
  
 
|-
 
|-
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Type:''' doublelist '''''inside square brackets '''''one''' and press '''Enter'''
 
Type:''' doublelist '''''inside square brackets '''''one''' and press '''Enter'''
  
We can see the output as '''b c d '''within square brackets
+
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.  
+
This is because the '''index value one''' contains the '''list''' inside a '''list''' as its '''element'''.  
  
 
|-
 
|-
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;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:0.079cm;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:0.079cm;padding-right:0.191cm;"| Now let us try to access a specific element, say''' b''' from the list inside a list  
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Now let us try to access a specific '''element''', say''' b''' from the '''list''' inside a '''list'''.
  
 
For this type: '''doublelist''''' inside square brackets ''one ''inside square brackets '''''zero '''and press '''Enter'''.
 
For this type: '''doublelist''''' inside square brackets ''one ''inside square brackets '''''zero '''and press '''Enter'''.
  
Here the 1st parameter represents the index of the list in the main list
+
Here the 1st '''parameter''' represents the '''index''' of the '''list''' in the main '''list'''.
  
The second parameter represents the index value of '''b''' in the list inside the list
+
The second '''parameter''' represents the '''index value''' of '''b''' in the '''list''' inside the '''list'''.
  
 
|-
 
|-
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'''<nowiki>doublelist=[‘a’, [‘b’,’c’,’d’], 'and', </nowiki>5, 6, 7, 8] '''
 
'''<nowiki>doublelist=[‘a’, [‘b’,’c’,’d’], 'and', </nowiki>5, 6, 7, 8] '''
  
# What is the command to get the element 'and' in the list doublelist?  
+
# What is the command to get the '''element 'and'''' in the '''list ''doublelist'''''?  
# How would you get 'and' using negative indices?  
+
# How would you get ''''and'''' using negative '''indices'''?  
# How would you get element 'd' from the list doublelist?  
+
# How would you get '''element 'd'''' from the '''list ''doublelist'''''?  
  
 
|-
 
|-
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Solution 2  
 
Solution 2  
  
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| The solution is on your screen  
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| The solution is on your screen.
  
 
|-
 
|-
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| '''slide len function'''
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| '''slide len function'''
  
'''len''' function is used to check the number of '''elements''' in the '''list'''.
+
'''len function''' is used to check the number of '''elements''' in the '''list'''.
  
 
Syntax:
 
Syntax:
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len(variable)
 
len(variable)
  
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| We can use '''len''' function to check the number of '''elements/length of '''in the '''list'''.
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| We can use '''len function''' to check the number of '''elements/length of '''in the '''list'''.
  
The syntax is: len ''inside'' ''parentheses ''variable
+
The syntax is: '''len''' ''inside parentheses '''''variable'''
  
 
|-
 
|-
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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Let us find the number of elements in '''mylist''' which we created earlier.  
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Let us find the number of elements in '''mylist''' which we created earlier.  
  
Switch to the''' terminal '''and clear the screen
+
Switch to the''' terminal '''and clear the screen.
  
 
Recall '''mylist''' by pressing up arrow key and press''' Enter.'''
 
Recall '''mylist''' by pressing up arrow key and press''' Enter.'''
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Type '''len '''''inside parentheses '''''mylist '''and press '''Enter.'''
 
Type '''len '''''inside parentheses '''''mylist '''and press '''Enter.'''
  
We get the length of mylist as '''four'''
+
We get the length of '''mylist''' as '''four'''.
  
 
|-
 
|-
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| '''Slide Append function'''
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| '''Slide Append function'''
  
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| We can append elements to the list using the '''append''' function.  
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| We can append '''elements''' to the '''list''' using the '''append function'''.  
  
This function will add the element to the end of the list.
+
This '''function''' will add the '''element''' to the end of the '''list'''.
  
The syntax is: variable ''dot'' '''append''' within ''parentheses element to be added.''
+
The syntax is: '''variable''' ''dot'' '''append''' within ''parentheses '''element''' to be added.''
  
 
|-
 
|-
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Now type  
 
Now type  
  
'''mylist''''' dot'' append ''inside parentheses within quotes''' ''sharp''' and''' '''press '''Enter'''.  
+
'''mylist''''' dot'' '''append''' ''inside parentheses within quotes''' ''sharp''' and''' '''press '''Enter'''.  
  
Type''' mylist '''''dot'' append ''inside parentheses''' ''six'' '''''and''' '''press '''Enter.'''
+
Type''' mylist '''''dot'' '''append''' ''inside parentheses''' ''six'' '''''and''' '''press '''Enter.'''
  
Let us check the''' '''updated''' mylist.'''
+
Let us check the '''updated mylist.'''
  
Type''' mylist '''and''' '''press '''Enter '''
+
Type''' mylist '''and press '''Enter '''
  
 
We can see '''mylist''' is '''appended''' with '''sharp''' and '''six''' at the end.
 
We can see '''mylist''' is '''appended''' with '''sharp''' and '''six''' at the end.
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|-
 
|-
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| '''slide del '''
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| '''slide del '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| We can also remove '''elements''' from '''Lists'''.  
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| We can also remove '''elements''' from '''lists'''.  
  
 
There are two ways of doing it.  
 
There are two ways of doing it.  
  
* One is by using the '''index '''with''' del''' keyword.  
+
* One is by using the '''index '''with''' del keyword'''.  
* Syntax is '''del '''variable ''inside square brackets element’s ''index value
+
* Syntax is '''del '''variable ''inside square brackets '''element’s ''index value'''.
  
 
|-
 
|-
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| '''slide remove'''
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| '''slide remove'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| * The other way is removing element by the value using remove function
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"|  
 +
* The other way is removing '''element''' by the value using '''remove function'''
 
* Syntax is '''variable '''''dot '''''remove '''''inside parentheses '''''element to be removed'''
 
* Syntax is '''variable '''''dot '''''remove '''''inside parentheses '''''element to be removed'''
  
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'''mylist '''
 
'''mylist '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Switch to the''' terminal '''
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Switch to the''' terminal.'''
  
Type '''mylist''' and press''' Enter '''to see the updated list
+
Type '''mylist''' and press''' Enter '''to see the updated '''list'''.
  
 
Type '''del '''''space '''''mylist '''''inside square brackets''''' one '''and press '''Enter.'''
 
Type '''del '''''space '''''mylist '''''inside square brackets''''' one '''and press '''Enter.'''
  
The keyword '''del''' deletes the element at '''index''' one,  
+
The '''keyword del''' deletes the '''element''' at '''index''' one,  
  
i.e the second element of the list,''' eggs'''.
+
i.e the second '''element''' of the '''list, eggs'''.
  
Again type '''mylist''' and press''' Enter'''
+
Again type '''mylist''' and press''' Enter'''.
  
We can see that the element '''eggs''' has been deleted from the list
+
We can see that the '''element eggs''' has been deleted from the '''list'''.
  
 
|-
 
|-
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'''mylist'''
 
'''mylist'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Let us delete the element '''hundred''' from '''mylist''' list.  
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Let us delete the '''element hundred''' from '''mylist list'''.  
  
For this we can use the '''function''' '''remove'''.
+
For this we can use the '''function remove'''.
  
 
Type '''mylist''''' dot '''''remove '''within parentheses''' hundred '''and press '''Enter.'''
 
Type '''mylist''''' dot '''''remove '''within parentheses''' hundred '''and press '''Enter.'''
  
Let us check the''' '''updated''' mylist.'''
+
Let us check the '''updated mylist.'''
  
 
|-
 
|-
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Type  
 
Type  
  
'''mylist''''' dot '''''append '''within parentheses within quotes '''spam '''and press''' enter'''
+
'''mylist''''' dot '''''append '''within parentheses within quotes '''spam '''and press''' Enter'''
  
'''Type mylist '''and press''' Enter'''
+
Type '''mylist '''and press''' Enter'''
  
Here is the''' '''updated''' mylist.'''
+
Here is the '''updated mylist.'''
  
It contains the element '''spam''' twice.
+
It contains the '''element spam''' twice.
  
One is at the start and the next is at the end of the list.
+
One is at the start and the next is at the end of the '''list'''.
  
 
|-
 
|-
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Type''' mylist '''
 
Type''' mylist '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Now remove the element '''spam''' by typing:
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Now remove the '''element spam''' by typing:
  
 
'''mylist '''''dot '''''remove '''''inside parentheses inside quotes'' '''spam '''and press '''Enter.'''
 
'''mylist '''''dot '''''remove '''''inside parentheses inside quotes'' '''spam '''and press '''Enter.'''
  
Let us check''' '''updated''' mylist.'''
+
Let us check '''updated mylist.'''
  
 
|-
 
|-
Line 431: Line 434:
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| We can see that only the first occurrence of ''''spam'''' has been removed.
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| We can see that only the first occurrence of ''''spam'''' has been removed.
  
The function '''remove''' removes the first occurrence of the element in the '''sequence'''.
+
The '''function remove''' removes the first occurrence of the '''element''' in the sequence.
  
Remember, the '''del '''keyword removes the element by index value.
+
Remember, the '''del keyword''' removes the '''element''' by '''index value'''.
  
'''remove '''function removes on the basis of element being passed on.  
+
'''remove function''' removes on the basis of '''element''' being passed on.  
  
 
|-
 
|-
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"|  
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"|  
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Using '''remove''' function, we can also remove an element with its index value  
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Using '''remove function''', we can also remove an '''element''' with its '''index value'''.
  
 
Let us try this with an example.  
 
Let us try this with an example.  
Line 453: Line 456:
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Type''' k '''''is equal to inside square brackets '''''one''''' comma '''''two''''' comma '''''one''''' comma '''''three '''and press''' Enter'''  
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Type''' k '''''is equal to inside square brackets '''''one''''' comma '''''two''''' comma '''''one''''' comma '''''three '''and press''' Enter'''  
  
'''then type k '''''dot remove inside parentheses''''' k inside square brackets two '''and press''' Enter'''
+
Then type '''k '''''dot '''remove''' inside parentheses''''' k inside square brackets two '''and press''' Enter'''
  
Type''' k '''and''' '''press '''Enter '''
+
Type''' k '''and press '''Enter '''
  
 
We can see the output as'''<nowiki> [2,1,3]. </nowiki>'''
 
We can see the output as'''<nowiki> [2,1,3]. </nowiki>'''
Line 468: Line 471:
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video.
  
1. Delete the fourth element from the list doublelist.
+
1. Delete the fourth '''element''' from the '''list doublelist'''.
  
2. Remove 'and' from the list doublelist.  
+
2. Remove ''''and'''' from the '''list doublelist'''.  
  
 
|-
 
|-
Line 484: Line 487:
 
Summary slide  
 
Summary slide  
  
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| This brings us to the end of this tutorial. In this tutorial, we have learnt to,''' '''
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.  
  
* '''Create:'''
+
In this tutorial, we have learnt to create:
** List with elements
+
* '''List''' with '''elements'''
** Empty list
+
* '''Empty list'''
** List within a list  
+
* '''List''' within a '''list'''
  
 
|-
 
|-
Line 495: Line 498:
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| We also learnt to,  
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| We also learnt to,  
  
* Find out the '''list''' length using '''len''' '''function'''.
+
* Find out the '''list''' length using '''len function'''.
 
* Access '''elements''' using their '''index''' numbers.  
 
* Access '''elements''' using their '''index''' numbers.  
* Append '''elements''' to list using the '''function''' '''append'''.  
+
* Append '''elements''' to '''list''' using the '''function append'''.  
* Delete '''element''' from list using the '''del''' and '''remove''' function
+
* Delete '''element''' from list using the '''del''' and '''remove function'''
  
 
|-
 
|-
Line 507: Line 510:
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve  
 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve  
  
# How do you create an empty list?  
+
# How do you create an '''empty list'''?  
# Can you have a list inside a list?  
+
# Can you have a '''list''' inside a '''list'''?  
# How would you access the last element of a list without finding its length?  
+
# How would you access the last '''element''' of a '''list''' without finding its length?  
  
 
|-
 
|-
Line 516: Line 519:
 
Solutions  
 
Solutions  
  
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| And the answers,''' '''
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| And the answers,  
  
# We create an empty list just by leaving the space inside the square brackets empty. '''myemptylist''' ''equal to open and close square brackets''.
+
# We create an '''empty list''' just by leaving the space inside the square brackets empty.  
# Yes, list can contain all the other data types, including list.  
+
#:'''myemptylist''' ''equal to open and close square brackets''.
# Using negative indices, we can access the last element from the list.
+
# Yes, '''list''' can contain all the other '''data types''', including '''list'''.  
 +
# Using negative '''indices''', we can access the last '''element''' from the '''list'''.
  
 
|-
 
|-
Line 544: Line 548:
  
 
Thank You
 
Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| This is _________ from IIT Bombay signing off.
+
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off.
  
Thank You
+
Thank you.
  
 
|}
 
|}

Latest revision as of 08:45, 8 September 2017

Python/C2/Getting Started with Lists/English

Title of script: Getting Started with Lists

Author: Aditya Palaparthy

Keywords: Python, IPython, list, del, remove, append

Visual Cue
Narration
Show Title Slide Hello Friends. Welcome to the tutorial on "Getting started with lists".
Show Slide

Objectives

At the end of this tutorial, you will be able to,
  • Create lists
  • Access list elements
  • Append elements to lists
  • Delete elements from lists
Show slide

System Specifications

To record this tutorial, I am using
  • Ubuntu Linux 14.04 operating system
  • Python 3.4.3
  • IPython 5.1.0
Show Slide

Pre-requisites

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.

Show Slide

List

What is a List?
  • A List can store a sequence of elements.
  • All elements need not be of the same data types
[Terminal]

ipython3

Let us open the Terminal by pressing Ctrl+Alt+T keys simultaneously

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.

[IPython Terminal]

mylist = ['spam', 'eggs', 100, 1.234]

Highlight spam and eggs

Let us define a list with a variable name mylist

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.

In Python, strings are always placed inside single or double quotes.

type(mylist)

Highlight the command

Now enter type within brackets mylist and press Enter.

Here type is a function which will return the datatype of the variable.

mylist is a list datatype.

Highlight according to narration 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.
Show slide

What is a variable?

  • variable must either start with an alphabet or an underscore.
  • They cannot start with numbers and cannot be the same as Python keywords.
In the code typed earlier, the name mylist is a variable.

In Python, a variable must either start with an alphabet or an underscore.

They cannot start with numbers and cannot be the same as Python keywords.

Examples of Keywords:
  • for, if, else, elif, while, in, def, or, and
  • A variable name cannot have spaces or punctuation characters or any arithmetic characters.
You will learn about keywords as we proceed.

Few examples of keywords are “for, if, else, elif, while, in, def, or, and”.


A variable name cannot have spaces or punctuation characters or any arithmetic characters.

show slide

Valid and invalid variables

Valid variable names:

  • x, y, xx, abc, a_b_c, a1, variable1, mylist, _x
  • foreign, spiff, while_true, or_else, and_od_else_1

Invalid names:

  • 1_x, 2_var, x-, x+, x;, x:
  • x y, x+y x*y x&^ae
  • for, in, elif
These are some of the valid and invalid variable names.
Switch to the terminal

Highlight mylist = ['spam', 'eggs', 100, 1.234]

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

x equal to inside square brackets inside quotes a comma inside quotes b and press Enter

Any valid variable name could be used.

[IPython Terminal]

myemptylist = []

Let us now create an empty list with no elements.

Type myemptylist is equal to open and close square brackets and press Enter.

This is an empty list without any element

slide

list index

We can access an element of a list using its corresponding index or position.

Index value of the elements starts from 0, 1, 2 and so on.

Negative indices are used to access elements from the end.

Which starts from -1, -2, and so on

The syntax to get a specific list element is

variable inside square brackets elements index value

Switch to the terminal.
[IPython Terminal]

mylist[0]

mylist[1]

mylist[3]

Type mylist inside square brackets zero and press Enter.

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

Type mylist inside square brackets one and press Enter.

mylist[1] gives the second element.

Show Slide

Exercise1

Pause the video. Try this exercise and then resume the video.

What happens when you type mylist[-1].

[IPython Terminal]

mylist[-1]

Switch to the terminal for solution

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.

slide

List in list

We can also create a list inside a list.

This property makes lists heterogeneous data structures.

This is the syntax for list inside a list.

[IPython Terminal]

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

Highlight [‘b’,’c’,’d’]

Let us include a list within a list for the variable doublelist.

Type the code as shown here:

Here b c d is a list in list which is represented within square brackets inside a list.

Type: doublelist[1] and press Enter Now let us fetch some element from doublelist.

Type: doublelist inside square brackets one and press Enter

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.

Highlight according to narration Now let us try to access a specific element, say b from the list inside a list.

For this type: doublelist inside square brackets one inside square brackets zero and press Enter.

Here the 1st parameter represents the index of the list in the main list.

The second parameter represents the index value of b in the list inside the list.

Show Slide

Exercise2

Pause the video. Try this exercise and then resume the video.

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

  1. What is the command to get the element 'and' in the list doublelist?
  2. How would you get 'and' using negative indices?
  3. How would you get element 'd' from the list doublelist?
Show Slide

Solution 2

The solution is on your screen.
slide len function

len function is used to check the number of elements in the list.

Syntax:

len(variable)

We can use len function to check the number of elements/length of in the list.

The syntax is: len inside parentheses variable

[IPython Terminal]

len(mylist)

Let us find the number of elements in mylist which we created earlier.

Switch to the terminal and clear the screen.

Recall mylist by pressing up arrow key and press Enter.

Type len inside parentheses mylist and press Enter.

We get the length of mylist as four.

Slide Append function We can append elements to the list using the append function.

This function will add the element to the end of the list.

The syntax is: variable dot append within parentheses element to be added.

[IPython Terminal]

mylist.append('sharp')

mylist.append(6)

Switch to the terminal

Now type

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

Type mylist dot append inside parentheses six and press Enter.

Let us check the updated mylist.

Type mylist and press Enter

We can see mylist is appended with sharp and six at the end.

slide del 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.
slide remove
  • The other way is removing element by the value using remove function
  • Syntax is variable dot remove inside parentheses element to be removed
mylist

[IPython Terminal]

del mylist[1]

mylist

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.

The keyword del deletes the element at index one,

i.e the second element of the list, eggs.

Again type mylist and press Enter.

We can see that the element eggs has been deleted from the list.

[IPython Terminal]

mylist.remove(100)

mylist

Let us delete the element hundred from mylist list.

For this we can use the function remove.

Type mylist dot remove within parentheses hundred and press Enter.

Let us check the updated mylist.

[IPython Terminal]

mylist.append('spam')

Highlight spam

What if the elements are repeated?

To check that, let’s do a small experiment.

Type

mylist dot append within parentheses within quotes spam and press Enter

Type mylist and press Enter

Here is the updated mylist.

It contains the element spam twice.

One is at the start and the next is at the end of the list.

mylist.remove('spam')

Type mylist

Now remove the element spam by typing:

mylist dot remove inside parentheses inside quotes spam and press Enter.

Let us check updated mylist.

Pause for a while We can see that only the first occurrence of 'spam' has been removed.

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.

Using remove function, we can also remove an element with its index value.

Let us try this with an example.

[Ipython Terminal]

k = [1,2,1,3]

k.remove(k[2])

k

Type k is equal to inside square brackets one comma two comma one comma three and press Enter

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].

Since it deletes the first occurrence of what is returned by k inside square brackets two which is one.

Show Slide

Exercise 3

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.

Show Slide

Exercise 3

The solution is on your screen.
Show Slide

Summary slide

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
We also learnt to,
  • Find out the list length using len function.
  • Access elements using their index numbers.
  • Append elements to list using the function append.
  • Delete element from list using the del and remove function
Show Slide

Evaluation

Here are some self assessment questions for you to solve
  1. How do you create an empty list?
  2. Can you have a list inside a list?
  3. How would you access the last element of a list without finding its length?
Show Slide

Solutions

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.
  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.
Show Slide: Forum Please post your timed queries in this forum.
Show Slide: Fossee Forum Please post your general queries on Python in this forum.
Show Slide: Textbook Companion FOSSEE team coordinates the TBC project.
Show Slide: Acknowledgement Spoken-tutorial is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

Show Slide

Thank You

This is Trupti Kini from IIT Bombay signing off.

Thank you.

Contributors and Content Editors

Nancyvarkey, Trupti