Python Nested List Explained With Examples

A nested list is made up of a series of sublists separated by commas.

Example:

L = ['a', ['b', ['c', 'd'], 'e', 'f'], 'g', 'h']

The following are the indices for the entries in a nested list:

List1 = ['a', 'b', ['c', 'd', ['e', 'f']], 'g', 'h']

print(List1[2])

Output: 

Output:

Output:

Negative indexing can also be used to reach a nested list.

Negative indexes work backwards from the list's end. As a result, L[-1] denotes the final item, L[-2] the second-to-last, and so on.

The negative indices for the elements in a nested list are shown in the following example:

List1 = ['a', 'b', ['c', 'd', ['e', 'f']], 'g', 'h']

print(List1[-3])

Output:

Output:

Output:

By referring to the index number of a specific item in a hierarchical list, you may modify its value.

List1 = ['a', ['b', 'c'], 'd']

List1[1][1] = 0

print(List1)

Output:

Use the append() method to add additional values to the end of the nested list.

List1= ['a', ['b', 'c'], 'd']

List1[1].append('x')

print(List1)

Output:

Use insert() method to add an element at a given place in a nested list.

List1= ['a', ['b', 'c'], 'd']

List1[1].insert(0,'x')

print(List1)

Output:

Using the extend() method, you can combine two lists into one.

List1 = ['a', ['b', 'c'], 'd']

List1[1].extend([1,2,3])

print(List1)

Output:

The pop() method can be used if you know the index of the object you desire. It changes the list and replaces the item that was removed.

List1 = ['a', ['b', 'c', 'd'], 'e']

x = List1[1].pop(1)

print(List1)

print(x)

You can use the del function in case there is no need for the removed value.

List1 = ['a', ['b', 'c', 'd'], 'e']

del List1[1][1]

print(List1)

In case you aren't sure about the location of an item in the list, you can use the remove() function to delete it by value.

List1 = ['a', ['b', 'c', 'd'], 'e']

List1[1].remove('c')

print(List1)

The built-in len() method may be used to determine the number of items in a nested sublist.

List1= ['a', ['b', 'c'], 'd']

print(len(List1))

Output:

print(len(List1[1]))

Output:

Use the basic for loop to traverse over the entries in a nested list.

List1 = [[1, 2, 3],[4, 5, 6],[7, 8, 9]]   

for list1 in List1:

    for number in list1:

        print(number, end=' ')

Output: