[Python-Dev] Organization of ABC modules

[Jeffrey Yasskin]

On Jan 25, 2008 9:31 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:
> Raymond Hettinger wrote:
> >> If you want ABCs to be more easily recognizable
> >> as such, perhaps we could use a naming convention,
> >
> > Essentially, that's all I was asking for.  It doesn't
> > really matter to me whether numbers.py gets called
> > abc_numbers or abc.numbers.  Either one would be an
> > improvement.
>
> I think the module level is the wrong granularity to be thinking about
> this - look at a module like collections, which contains not only ABC's
> related to containers, but also some useful concrete containers like
> deque and namedtuple.
>
> Any naming convention would have to be at the class level. For example:
>
> class NumberABC(metaclass=ABCMeta):
>     ...
>
> class ComplexABC(NumberABC):
>     ...
>
> class RealABC(ComplexABC):
>     ...
>
> class RationalABC(NumberABC):
>     ...
>
> class IntegralABC(RationalABC):
>     ...
>
> I think adopting such a convention (at least for the standard library)
> would actually be useful. Normally, finding isinstance() type checks in
> code bothers me severely as it usually indicates that duck-typing has
> been broken. On the other hand, if I find a check in code that does
> something like:
>
>    if not isinstance(x, NumberABC):
>       raise TypeError("Not a number!")
>
> it would clearly still be extensible, as I would know just from the
> naming convention that a third party can register their type with
> NumberABC to make it usable with this function.
>
> Without a naming convention, I would always have to go check the
> definition of the type in the isinstance() call to see if the code was
> legitimate.

That's a good point. Someone already convinced me to name the test for
numbers.py, test_abstract_numbers.py, so renaming the module makes
sense too, although I agree that collections, which contains some
concrete classes, should keep its current name. If others agree, want
to send a patch?

-- 
Namasté,
Jeffrey Yasskin