stylistic question -- optional return value

Peter Hansen peter at
Thu Aug 29 00:39:55 CEST 2002

Andrew Koenig wrote:
> Suppose I have a function that sometimes returns one value and sometimes
> returns two.  What's the cleanest way to define such an interface?
> However, I can obtain the same information content by returning
> (x,) or (x, y).  However, I can easily imagine people becoming
> confused by 1-tuples.

Can you imagine them becoming confused by 1-lists?  Why not just
return a list, always, with one or more items in it.  len() is
available to check which you have if you need it.

> What is the most Pythonic way of solving this problem?

Personally, I'd probably use a list because I eschew tuples most
of the time.  In this case, if I thought I wanted a tuple, I would
return a tuple and assume no one would get confused by them.

The only time I imagine someone getting confused by a 1-tuple
is when someone is expected to create one to pass *in* to my
functions, not when my function is returning one.

Maybe I'm wrong about that, but I've never heard of anyone being
confused upon receiving a 1-tuple.

Definitely, in my opinion, all the other suggestions including
sentinels and special classes, are much less Pythonic than a
nice simple list or tuple.


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