PYTHON - NESTED LIST

'Nested Lists' are the one in which, a block of List can contain another List.

Say for example, let us take the below List.

So, if you see the second location or index/position '1' of the above List. There is another List of two elements containing the names 'Satyam' and 'Rishab' stored in it.

This List is an example of 'Nested List'.

How to create and access the elements of Nested Lists ?

Let us create the above 'Nested List'.

Example :

x = ["Mohan", [ "Satyam", "Rishab"] , "Paul", "Kriti", "Salim"]
print("The first element of the nested List is ", x[1][0])
print("The second element of the nested List is ", x[1][1])

Output :

The first element of the nested List is Satyam
The second element of the nested List is Rishab

So, in the above example, we have declared a Nested List and initialised it to 'x'.

x = ["Mohan", [ "Satyam", "Rishab"] , "Paul", "Kriti", "Salim"]

Now, let us see the diagram,

And as we can see, the names 'Satyam' and 'Rishab' is located at the second location of 'x'.

So, to access 'Satyam', we need to goto index '1' of the List and then goto the index of 'Satyam' i.e. Index '0'.

i.e. x[1][0]

And thus the print statement prints 'Satyam'.

print("The first element of the nested List is ", x[1][0])

Similarly, to access 'Rishab', we need to goto index '1' of the List and then goto the index of 'Rishab' i.e. Index '1'.

i.e. x[1][1]

And thus the print statement prints 'Satyam'.

print("The second element of the nested List is ", x[1][1])

A deeper Nested List

Now, what if we want to find out the first letter of 'Rishab' or the second letter of Paul.

Example :

x = ["Mohan", [ "Satyam", "Rishab"] , "Paul", "Kriti", "Salim"]
print("The first letter of Rishab is ", x[1][1][0])
print("The second letter of Paul is ", x[2][1])

Output :

The first letter of Rishab is R
The second letter of Paul is a

So, in the above example, we have declared a Nested List and initialised it to 'x'.

x = ["Mohan", [ "Satyam", "Rishab"] , "Paul", "Kriti", "Salim"]

So, we have the same diagram,

Similarly, to access the first letter of i.e. 'R' of 'Rishab',

We need to goto 'Rishab'

And as we have seen, to access 'Rishab', we need to goto index '1' of the List and then goto the index of 'Rishab' i.e. Index '1'.

Which would be 'x[1][1]'. And 'x[1][1]' is the location where 'Rishab' lies.

Now, if we further subdivide 'Rishav'. It would be,

And the 'R' of 'Rishav' lies in the '0'th location.

So, the finally to reach 'R' of 'Rishav', the location is 'x[1][1][0]'.

Where 'x[1][1]' is the location of 'Rishav' and '0' is the location of 'R'. Which is 'x[1][1][0]'.

And thus the print statement, prints the first letter of 'Rishav'.

print("The first letter of Rishab is ", x[1][1][0])

And the same way, the print statement prints the second letter of 'Paul', i.e. 'a'.

print("The second letter of Paul is ", x[2][1])

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