Recursion

A recursive function is a function that calls itself to solve a smaller piece of a larger problem. It is like looking into a mirror that's looking into another mirror.

Every recursive function MUST have a Base Case. This is the termination logic that stops the execution; without it, the function will call itself forever and crash with a RecursionError (Stack Overflow).

def factorial(n):
    # Base case: stop when n is 0
    if n == 0:
        return 1
    # Recursive step: n * (n-1)!
    return n * factorial(n - 1)

print(factorial(5))

Output:

120