Nested List Input in Python: A Beginner’s Guide

Nested lists are a powerful data structure in Python. In this article, we will explore how to take input for a nested list in Python. Let’s consider the following example: [[‘B’, 21], [‘C’, 26], [‘A’, 34]]

To input elements for a nested list, we can use loops. Firstly, we need to create two lists — one for the final list and another for the sub-list. Then, we can use nested for loops to take input for the elements of the sub-list and append it to the final list.

In the outer loop, we need to iterate through the number of sub-lists in the list. In the inner loop, we can take input for the elements of the sub-list. After every iteration of the outer loop, we need to set the temporary list to null to avoid any previous values.

Here’s the code:

# Initialize an empty list to store the final output
my_list = []

# Initialize an empty temporary list to store each sub-list
temp_list = []

# Take input from the user for the number of sub-lists
n = int(input('Enter the number of sub-lists: '))

# Loop over the range of n to take input for each sub-list
for i in range(n):
    
    # Loop over the range of 2 to take input for each element in the sub-list
    for j in range(2):
        
        # Take input from the user for the current element
        temp_list.append(input())
    
    # Append the current sub-list to the final list
    my_list.append(temp_list)
    
    # Reset the temporary list to an empty list for the next iteration
    temp_list = []

# Print the final output
print(my_list)

Explanation:

• First, we initialize an empty list my_list to store the final output, and an empty temporary list temp_list to store each sub-list.
• Then, we take input from the user for the number of sub-lists using input() and convert it to an integer using int(), and store it in the variable n.
• Next, we loop over the range of n using for i in range(n): to take input for each sub-list.
• Within this loop, we loop over the range of 2 using for j in range(2): to take input for each element in the sub-list.
• We take input from the user for the current element using input() and append it to the temporary list using temp_list.append(input()).
• After we have taken input for all elements in the sub-list, we append the current sub-list to the final list using my_list.append(temp_list).
• We then reset the temporary list to an empty list for the next iteration using temp_list = [].
• Finally, we print the final output using print(my_list).

OUTPUT:

Enter the size of the list: 3
a
21
b
34
c
76
Input List: [['a', '21'], ['b', '34'], ['c', '76']]

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