Estimating PI using the algorithm from Srinivasa Ramanujan

estimate_python.py

import math

def factorial(n):
    if n == 0:
        return 1
    else:
        result = n * factorial(n-1)
        return result
    
def estimate_pi():
    total = 0
    k = 0
    factor = 2 * math.sqrt(2) / 9801

    while True:
        num = factorial(4*k) * (1103 + 26390 * k)
        den = factorial(k) ** 4 * 396 ** (4*k)

        total += num / den
        term = factor * num/den

        if abs(term) < 1e-15:
            break

        k += 1

    return factor * total

print(estimate_pi())

http://en.wikipedia.org/wiki/Pi