Как вичеслять факториал на Python?

1 - n = input ("Факториал числа ") n = int (n) fac = 1 i = 0 while i < n: i + = 1 fac = fac * i print ("равен", fac)

2 - import operator def fact (n) : return reduce (operator. mul, xrange (1, n + 1), 1) print fact (5)

3 - import math math. factorial (5)