len() should always return something

[Diez B. Roggisch]

Dr. Phillip M. Feldman schrieb:
> Here's a simple-minded example:
> 
> def dumbfunc(xs):
>    for x in xs:
>       print x
> 
> This function works fine if xs is a list of floats, but not if it is single
> float.  It can be made to work as follows:
> 
> def dumbfunc(xs):
>    if isinstance(xs,(int,float,complex)): xs= [xs]
>    for x in xs:
>       print x
> 
> Having to put such extra logic into practically every function is one of the
> annoying things about Python.

And where comes "len(xs)" into play here? What you want is iteration 
over scalars.

I do think that if you frequently have to write code like that, you are 
writing errorneous code.

But might that as it is, a simple


def iterable(i):
     if isinstance(i, (int, float, complex)):
        return [i]
     return i


is all you need. So you can write


for x in iterable(xs):


wherever you expect values to be either scalar or iterable.

Diez