2012年11月25日

#! /usr/bin/env python

# coding: utf-8

def factorial(number):

    i = 2

    result = 1

    while i <= number :

        result = result*i

        i+=1

    else:

        return result

while True :

    num = raw_input('this is where you type(number or exit):')

    while not num.isdigit():

        if num == 'exit' :

            raise SystemExit

        num = raw_input('Wrong input, try again:')

    else:

        print "\nthe result of factorial is",factorial(int(num)),"\n"