What's wrong with my code in Python 2.7.9?

Question

I have just started learning python and written a procedure to calculate factorial of a number. I am getting a logical error. The value returned by fact function is None and the value of factorial after execution is 24.

factorial = 1

def fact(num) :
    if num == 0 :
        return 1
    global factorial
    print factorial
    factorial *= num
    if num-1 > 1 :
        fact(num - 1)
    else :
        return factorial

print fact(4)
print factorial

Output :

1
4
12
None
24

You should return the recursive call's return value, return fact(num - 1). You might also want to look at this answer — thefourtheye
– thefourtheye, Commented Sep 16, 2015 at 18:42
possible duplicate of Recursive function does not return specified value — Barmar
– Barmar, Commented Sep 16, 2015 at 18:51

Bonifacio2 · Accepted Answer · 2015-09-16 18:41:55Z

2

You should change

if num-1 > 1 :
    fact(num - 1)
else:
    return factorial

to:

if num-1 > 1 :
    return fact(num - 1)
else :
    return factorial

The problem was you were not returning anything except for the base case.

answered Sep 16, 2015 at 18:41

Bonifacio2

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