View source for Python-3.4.3/C2/Accessing-parts-of-arrays/English


{| style="border-spacing:0;"
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;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:0.097cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Welcome to the spoken tutorial on "'''Accessing parts of arrays'''". 

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Objectives 



| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| In this tutorial, we will learn to access and change:

* Individual '''elements''' of '''single dimensional''' and '''multi-dimensional '''arrays'''.
* '''Rows''' and '''columns''' of '''arrays'''. 
* '''Elements''' of an '''array''', using '''slicing''' and '''striding'''. 

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;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:0.097cm;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'''

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Pre-requisite slide 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to 

* run basic '''Python '''commands on the '''IPython console.'''
* use''' arrays.'''

If not, see the relevant '''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:0.097cm;padding-right:0.191cm;"| Show Slide

Sample Arrays



| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Let us begin with the help of an example. 


Consider two '''arrays''', A and C.


We will use these '''arrays''' throughout this tutorial. 

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| <nowiki>[Terminal]</nowiki>

Open the '''terminal''', type '''ipython3 '''and press '''Enter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Let us start '''ipython'''.


Open the '''terminal'''. 


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

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''import numpy as np'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Let us create the two '''arrays''' in '''terminal'''.


For this, we have to import '''numpy library'''.


Type '''import numpy as np''' and press '''Enter'''.


From here onwards, please remember to press the '''Enter''' key after typing every command on the '''terminal'''. 

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type, '''A = np.arange(1,6)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''A '''''is equal to''''' np '''''dot '''''arange '''''inside parentheses '''''1 '''''comma '''''6 '''

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''C = np.arange(1,26).reshape(5,5)'''


Highlight arange, reshape
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type, '''C '''''is equal to''''' np '''''dot '''''arange '''''inside parentheses '''''1 '''''comma '''''26 '''''dot '''''reshape '''''inside parentheses''''' 5 '''''comma '''''5 '''


We have already learnt about '''arange''' and''' reshape methods''' in an earlier tutorial.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''A'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Now, let us see the contents of A and C.


Type '''A '''

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type, '''C '''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''C '''

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Highlight

<nowiki>A = array([1, 2, 3, 4, 5])</nowiki>


<nowiki>C = array([[1, 2, 3, 4, 5]</nowiki>

<nowiki>[6, 7, 8, 9, 10],</nowiki>

<nowiki>[11, 12, 13, 14, 15], </nowiki>

<nowiki>[16, 17, 18, 19, 20],</nowiki>

<nowiki>[21, 22, 23, 24, 25]])</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| In '''A''', we have only one row with '''elements''' from 1 to 6.


'''A''' is a '''one dimensional array.'''


In '''C''', we have 1 to 26 '''elements''' in the form of '''matrix''' of 5 rows and 5 columns.


So '''C''' is a '''two dimensional array.'''


<nowiki><<PAUSE>></nowiki>

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| <nowiki>Highlight 3 in A = array([1, 2, 3, 4, 5])</nowiki>


Type '''<nowiki>A[2] </nowiki>'''



| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Next, let us see about '''accessing''' individual '''elements''' in an array.


To access, the '''element''' 3 in '''array A''', we say, A of 2.


Type '''A '''''inside square brackets '''''2'''


In '''Python, arrays''' are '''zero-indexed'''. 


This means, the position of the '''element''' starts with 0 instead of 1.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Highlight array C in slide


Type, '''<nowiki>C[2, 3]</nowiki>''' 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Now, let us access the '''element''' 14 from '''array C'''. 


14 is in the third '''row''' and the fourth '''column'''.


To do this, we say, C of 2,3.


Type '''C '''''inside square brackets '''''2 '''''comma''''' 3'''.


<nowiki><<PAUSE>></nowiki>

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Highlight array A, C in slide


Type '''<nowiki>A[2] = -3</nowiki>'''



| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Next we will learn how to change the value of an '''array'''.


We shall now change 3 to -3 in A and 14 to -14 in C. 


For this we simply assign the new value after accessing the '''element'''. 


Type, '''A '''''inside square brackets '''''2 '''''is equal to minus '''3 '''''

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type, '''<nowiki>C[2, 3] = -14</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type, '''C '''''inside square brackets '''''2 '''''comma''''' 3 '''''is equal to minus '''''14'''

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type, '''A'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Let us check our operations.


Type '''A'''

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type''' C'''


Highlight -3 and -14
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''C'''


You can see that the '''elements''' are changed now.


Likewise you can change any single '''element''' in an '''array'''.


<nowiki><<PAUSE>></nowiki>

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Highlight array C in slide


Type, '''<nowiki>C[2] </nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Next let us learn to change more than one '''elements''' at a time. 


First with '''rows '''and then with '''columns'''. 


Let us access one '''row''' of C, say the third '''row'''. 


Type '''C '''''inside square brackets '''''2'''


We can see that the third row of the '''array''' is displayed now.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Slide:

Negative Indexing



| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| '''Python programming''' supports '''negative indexing''' of '''arrays'''.


This means the index value of

* -1 gives the last element and 
* -2 gives the second to last element of an array.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''<nowiki>C[4] </nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| We can access the last '''row''' of C in 2 ways.


Type '''C '''''inside square brackets '''''4'''

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''<nowiki>C[-1]</nowiki>'''


Highlight the outputs
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Or with '''negative indexing''' as''' C '''''inside square brackets minus '''''1'''


Notice that both the outputs are same.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''<nowiki>C[-1] = [0, 0, 0, 0, 0]</nowiki>''' 



| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Now, we will learn to change the last '''row''' into all '''zeros.'''


Type '''C '''''inside square brackets minus ''1 is ''equal to''''' '''''inside square brackets 0 comma 0 comma 0 comma 0 comma 0''

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type''' C'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type''' C'''


Notice that zeros are displayed in the last row of the '''array''' C.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type'''<nowiki> C[-1] = 2</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| We can also type,''' C '''''inside square brackets minus '''''1 '''''is equal to''''' 2.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type C


Highlight the last row
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type C 


And check with the changes made.


<nowiki><<PAUSE>></nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Slicing slide


<nowiki>[start:stop]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Now let us learn to '''slice''' an '''array'''.


'''Slicing''' of an '''array''' is done to access parts of an '''array'''.


'''Slicing''' syntax is inside square brackets '''start colon stop.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Striding slide


syntax '''<nowiki>[start:stop:step]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| '''Striding''' uses the ‘step’ value to jump between the '''elements''' in an '''array'''.


'''Striding''' syntax is inside square brackets '''start '''colon '''stop colon step.'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Switch to terminal.
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Switch back to the '''terminal'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''<nowiki>C[0:3,2] </nowiki>'''


<nowiki>Highlight array([ 3, </nowiki>8, 13])
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type, '''C '''''inside square brackets '''''0 '''colon '''3 '''comma''' 2'''


0 and 3 corresponds to start and stop values for row '''slicing''' and 2 corresponds to column index.


We get the '''elements''' of '''rows indexed from 0 to 2 and column''' '''indexed''' by 2. 


Hence we have '''sliced''' the '''array'''.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| <nowiki>Highlight in C ([11, 12, 13])</nowiki>


Type '''<nowiki>C[2,0:3] </nowiki>'''


Highlight '''2 '''and '''0:3'''



| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Now we will access the '''elements''' of '''row''' with '''index''' 2, and first 2 columns.


Type '''C '''''inside square brackets '''''2''' comma''' 0 '''colon '''3'''


2 corresponds to row index and 0 and 3 corresponds to start and stop values for column '''slicing'''.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;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:0.097cm;padding-right:0.191cm;"| Pause the video. 


Try this exercise and then resume the video.


Obtain the following '''elements''' one by one from '''array''' C.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Switch to terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Switch to the '''terminal''' for the solution. 

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''<nowiki>C[1, 1:3]</nowiki>'''


<nowiki>Highlight[7,8]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''C '''''inside square brackets '''''1 '''comma''' 1 '''colon '''3'''


We get the '''elements''' 7 and 8.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''<nowiki>C[0:4, 0]</nowiki>''' 


<nowiki>Highlight [1, 6, 11, 16]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''C '''''inside square brackets '''''0 '''colon '''4 '''comma''' 0 '''


We get the '''elements''' 1, 6, 11 and 16

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''<nowiki>C[1:5, 0] </nowiki>'''


'''Highlight '''<nowiki>[6, 11, 16, 0]</nowiki>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''C '''''inside square brackets '''''1 '''colon '''5 '''comma''' 0'''


We get the '''elements''' 6, 11, 16 and 2

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''<nowiki>C[1:, 0]</nowiki>'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| We can also get the same elements by typing '''C '''''inside square brackets '''''1 '''colon comma''' 0'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;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:0.097cm;padding-right:0.191cm;"| Pause the video. 


Try this exercise and then resume the video.


Obtain the '''elements''' [[8, 9], [13, -14]] from '''array''' C.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Switch to terminal
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Switch to the '''terminal''' for the solution. 

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''<nowiki>C[1:3, 2:4]</nowiki>'''


Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type, '''C '''''inside square brackets '''''1 '''colon '''3 '''comma''' 2 '''colon '''4'''


We got the required '''elements'''. 


<nowiki><<PAUSE>></nowiki>

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''<nowiki>C[0:5:2, 0:5:2] </nowiki>'''



| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Next we will learn the idea of '''striding''' using the smaller '''array''' C. 


We will try to access only the odd rows and columns i.e first, third and fifth.


Type, '''C '''''inside square brackets '''''0 '''colon '''5 '''colon '''2 '''comma''' 0 '''colon '''5 '''colon '''2'''

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Type '''<nowiki>C[::2, ::2] </nowiki>'''


Highlight the output



| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| We can also type '''C '''''inside square brackets colon colon '''''2 '''comma colon colon''' 2 '''


We can see that only the odd rows and columns are displayed.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Highlight 2 in '''<nowiki>C[::2, ::2] </nowiki>'''


Type '''<nowiki>C[1::2, ::2] </nowiki>'''


Highlight the output
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| The '''step''' 2 specifies the '''jump''' between the '''elements'''. 


This is called '''striding'''.


If no '''step''' is specified, a default value of 1 is assumed. 


Type '''C '''''inside square brackets''''' 1 '''colon colon '''2 '''comma colon colon '''2 '''


We get the '''elements''' as shown.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;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:0.097cm;padding-right:0.191cm;"| Pause the video. 


Try this exercise and then resume the video.


Obtain the following '''elements''' from '''array''' C.

|-
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Show Slide Solution 3
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;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:0.097cm;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:0.097cm;padding-right:0.191cm;"| This brings us to the end of this tutorial. 


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


# Manipulate '''single''' and '''multi''' '''dimensional''' '''arrays'''. 
# Access and change individual '''elements''' by using their '''index numbers.'''
# Access and change '''rows''' and '''columns''' of arrays by specifying the '''row''' and '''column''' numbers. 
# '''Slice''' and '''stride''' on '''arrays'''. 

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Evaluation 



| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve.


# How do we access the '''element''' 18 from the given array A? 
# How do we obtain the '''elements''' <nowiki>[[21, 22], [31, 32]] </nowiki>from the given '''array''' B?

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Solutions 



| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| And the answers,

# The '''element''' 18 in '''array''' A has index number 2. Hence, we can access it as A of 2

# To obtain the central four numbers in the '''array''' B, we say, B ''inside square brackets ''1 colon 3 comma 1 colon 3

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Show Slide Acknowledgement 
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| Spoken-tutorial is funded by NMEICT, MHRD, Govt. of India. 


For more details, visit this website.

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Thank You
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.097cm;padding-right:0.191cm;"| This is Priya from IIT Bombay signing off. Thanks for watching.

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