Square numbers
Input
map_list([1, 2, 3], lambda x: x * x)
Output
[1, 4, 9]
Each element is replaced by its square.
Full lesson preview
Map a function over a list
Apply a function to each element of a list and return a new list of results.
Python practice16 minLists & TuplesIntermediateLast updated March 17, 2026
Problem statement
Given a list and a function that accepts a single argument, return a new list containing the result of applying the function to each element of the input list. Do not mutate the original list. The function may change the element type (e.g., int -> str).
Task
Implement map_list(lst, func) that returns a new list where each element is func(original_element).
Examples
Input format
A list (lst) and a single-argument callable (func).
Output format
A list of the same length where the i-th element is func(lst[i]).
Constraints
Do not use external libraries. Maintain order. Time complexity O(n).
Samples
Sample 1
Input
map_list(['a','b'], lambda s: s.upper())
Output
['A', 'B']
Each string is converted to uppercase.