Factorial of 4
Input
factorial(4)
Output
24
4! = 4 * 3 * 2 * 1 = 24; recursion reduces n until base case 0.
Full lesson preview
Implement a simple recursive function with a base case
Implement recursion with a clear base case by writing a factorial function.
Python practice17 minFunctions & ScopeIntermediateLast updated March 17, 2026
Problem statement
Implement factorial(n) that returns n! (n factorial) for non-negative integers using recursion. The base case is n == 0 which returns 1. Validate input: n must be an integer and non-negative; raise TypeError for non-integers and ValueError for negative integers. Use recursion for the general case.
Task
Write a recursive factorial(n) function that handles base cases and validates input.
Examples
Input format
A single integer n passed to factorial(n).
Output format
Return an integer equal to n!. The returned value will be converted to a string for comparison.
Constraints
Use recursion with a base case n == 0. Validate that n is a non-negative integer.
Samples
Sample 1
Input
factorial(5)
Output
120
5! = 120