just to prove a point

fac.py

#!/usr/bin/env python

def fac(n):
    if n == 0:
        return 0

    f = 0
    for i in reversed(xrange(n)):
        if f == 0:
            f = i+1
            continue
        f *= i+1
    return f


if __name__ == '__main__':
    print(fac(100000))

fac.rkt

#lang racket

(define (factorial n)
  (define (inside n sum)
    (if (= 0 n) sum
        (inside (- n 1) (* n sum))))
  (inside n 1))
(printf "~a~n" (factorial 100000))
;; racket fac.rkt  5.95s user 0.33s system 95% cpu 6.556 total