Homemade factorial function in Python

Question

I know a code that works, but I can't seem to figure out why this code only returns 0. Can anyone help me fix this?

def factorial(x):
    hold = 1
    count = x
    if x == 0:
        return 1
    else:
        while count > 0:
            count -= 1
            hold *= count
            return hold

I edited the post to make it more clear, also adding in @DanielA.White's suggestion. I still get the same problem. — user4326875
– user4326875, Commented Dec 5, 2014 at 1:37

Piotr Dabkowski · Accepted Answer · 2015-01-18 00:43:22Z

3

It returns 0 because count will be finally 0 in your last loop. Loop will execute for count = 1 and you will multiply hold by 0 since you subtract 1 from count before multiplying. You have to subtract 1 after multiplication:

def factorial(x):
    hold = 1
    count = x
    if x == 0:
        return 1
    else:
        while count > 0:
            hold *= count
            count -= 1  # moved this statement to the bottom
        return hold

However much better function would be:

def factorial(x):
   hold = 1
   for number in xrange(2, x+1): # or range in python 3
       hold *= number
   return hold

edited Jan 18, 2015 at 0:43

answered Dec 5, 2014 at 1:42

Piotr Dabkowski

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