CODEWITHSUNDEEP
python
baptist
baptist

Reputation: 29

Python Function returning null

def counter(number,count):
    if (number!=1 and number%2==0):
        a=number/2
        count=count+1
        counter(a,count)
    elif (number!=1 and number%2!=0):
        a=3*(number)+1
        count=count+1
        counter(a,count)        
    else:
        print count
        return count

z=counter(13,0)
print z

count is evaluated to 9 and it does print it, but won't return it? Says None when printing 'z'

Upvotes: 0

Views: 61

Answers (2)

Ignacio Vazquez-Abrams
Ignacio Vazquez-Abrams

Reputation: 798676

You forgot to return the result of recursion.

return counter(a,count)

Upvotes: 2

Martijn Pieters
Martijn Pieters

Reputation: 1121924

You are ignoring the recursive calls; add return statements where you call counter() in counter itself:

def counter(number,count):
    if (number!=1 and number%2==0):
        a=number/2
        count=count+1
        return counter(a,count)
    elif (number!=1 and number%2!=0):
        a=3*(number)+1
        count=count+1
        return counter(a,count)        
    else:
        print count
        return count

Recursive calls are just like any other function call, if you don't do anything with the return value it is just discarded. Recursive calls don't magically pass on their result to the outermost call.

Upvotes: 3

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