Function Returning None When Recursion Employed [duplicate]

Question

I'm sure I'm making a simple error but in my function looking to return the factorial of a user given input when the input isn't 1 or 0 it actually just returns none. I printed out what it was doing within the helper function and it looks like it obtained the proper result but when I run it as below it returns none. Please let me know what obvious oversight I'm making. Thanks.

def recurseFactorial(num, mySum):
    if num==0 or num==1:
        return mySum
    else:
        recurseFactorial(num-1,mySum=mySum*num)

while True:
    myInput = input("Please enter the number: ")
    print(recurseFactorial(int(myInput), 1))

Does this answer your question? Why does my recursive function return None? — VLAZ
– VLAZ, Commented Nov 3, 2022 at 17:35

John Gordon · Accepted Answer · 2018-08-31 01:27:28Z

3

In the else branch, you're calling recurseFactorial, but you're not returning its result. And since that branch has no return statement, it returns None by default.

You want this instead:

def recurseFactorial(num, mySum):
    if num==0 or num==1:
        return mySum
    else:
        return recurseFactorial(num-1,mySum=mySum*num)

answered Aug 31, 2018 at 1:27

John Gordon

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1 Comment

MPython Over a year ago

Worked like a charm. Thank you so much. Knew I was missing something easy. Appreciate it.

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