A recursive function is one that calls itself. Recursion is useful for solving problems that can be broken down into smaller, similar problems.

Example:

def fibonacci(n):
    if n <= 1:
        return n
    else:
        return fibonacci(n-1) + fibonacci(n-2)

print(fibonacci(6))

Output:

8

Real-world Example:

Vasanta Kumar uses recursion to compute the greatest common divisor (GCD):

def gcd(a, b):
    if b == 0:
        return a
    else:
        return gcd(b, a % b)

print(gcd(48, 18))

Output:

6

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