Nested Lists in Python
We know that a list is a collection of items separated by commas and enclosed within square brackets [ ]. The values stored in a list can be accessed using the slice operator ([ ] and [:]) with index position starting at 0 from the beginning of the list and in case of reverse accessing of list then the index position is -1.
Ex
>>> List=[1,2,”Python”]
>>> List [1, 2, ‘Python’] |
Now let us have a glance at nested lists.
Nested Lists
A nested list is a list that appears as an element in another list.
Ex
>>> nested_list=[1,2,3,[“Hi”,4.5],’abc’]
>>> nested_list [1, 2, 3, [‘Hi’, 4.5], ‘abc’] |
Here the element with index position 3 is a nested list.
Creating a nested list
Creating a nested list is almost similar as creating a list. Here, a list is considered as one of the elements in a nested list.
>>> n_list=[12,52,[“hi”,3.5],7]
>>> n_list [12, 52, [‘hi’, 3.5], 7] |
Adding elements into a Nested Lists
We can add elements into a list directly as shown in above. In case of nested lists we use append ( ) method to add elements in to it. For the same list we are going to add elements now.
>>> n_list.append([1,2,’orange’])
>>> n_list [12, 52, [‘hi’, 3.5], 7, [1, 2, ‘orange’]] |
Accessing elements from Nested Lists
We can access the elements from a nested list by using indexing ‘[ ]’. It is illustrated for the same above example.
>>> n_list
[12, 52, [‘hi’, 3.5], 7, [1, 2, ‘orange’]] >>> n_list[2] [‘hi’, 3.5] >>> n_list[2][1] 3.5 >>> n_list[0] 12 |
Updating a Nested List
The following example describes how to update a list in a nested list.
>>> n_list
[12, 52, [‘hi’, 3.5], 7, [1, 2, ‘orange’]] >>> n_list[1]=”VMS” >>> n_list [12, ‘VMS’, [‘hi’, 3.5], 7, [1, 2, ‘orange’]] |
Deleting elements in a Nested Lists
The following example describes how to delete an element in a nested list.
>>> n_list=[12, ‘VMS’, [‘hi’, 3.5], 7, [1, 2, ‘orange’]]
>>> n_list [12, ‘VMS’, [‘hi’, 3.5], 7, [1, 2, ‘orange’]] >>> del(n_list[3]) >>> n_list [12, ‘VMS’, [‘hi’, 3.5], [1, 2, ‘orange’]] >>> del(n_list[2]) >>> n_list [12, ‘VMS’, [1, 2, ‘orange’]] >>> del(n_list[2][2]) >>> n_list [12, ‘VMS’, [1, 2]] |
Iteration with elements in nested lists
We can iterate through every element in a nested list by using for loops. The below example describes the iteration of an element in nested list.
Output
12
VMS [‘hi’, 3.5] 7
12 VMS [‘hi’, 3.5] 7
12 VMS [‘hi’, 3.5] 7
12 VMS [‘hi’, 3.5] 7 |
Note
Here the output prints for four times because the elements in the list are 4 in count.