Why does my python function return none if I have a return for every case?

Question

I can't figure out why this returns none!

I have a return for every branch...

Thanks in advance.

def recurPowerNew(base, exp):
    '''
    base: int or float.
    exp: int >= 0

    returns: int or float; base^exp
    '''
    if exp<=0:
        return 1
    elif exp%2==0:
        return recurPowerNew(base*base, (exp/2))

        return base*recurPowerNew(base, (exp-1))


print recurPowerNew(7.62,9)

It isn't necessary here, but it's often clearer to use if/elif/else, instead of if/elif and then falling off the end of that statement. (That would also have made your actual bug impossible to write.) — abarnert
– abarnert, Commented Dec 18, 2013 at 21:40
Because you don't have a return for every branch. You have two returns for the second branch, and none for the third... — kindall
– kindall, Commented Dec 18, 2013 at 21:42

Paulo Bu · Accepted Answer · 2013-12-18 21:43:58Z

8

Because of your indentation, the last line of your input is wrong indented.

You should fix it to this:

def recurPowerNew(base, exp):
    """
    base: int or float.
    exp: int >= 0

    returns: int or float; base^exp
    """
    if exp <= 0:
        return 1
    elif exp%2 == 0:
        return recurPowerNew(base*base, (exp/2))

    return base*recurPowerNew(base, (exp-1))

While we're here, I'll like to point that according to PEP-257 it's better to use double quotes than single quotes:

For consistency, always use """triple double quotes""" around docstrings.

edited Dec 18, 2013 at 21:43

answered Dec 18, 2013 at 21:36

Paulo Bu

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