[Python-Dev] Making types behave like classes

[Paul Prescod]

Gordon McMillan wrote:
> 
>..
> 
> There's only one difference that matters: subclassing. I don't
> think there's an incremental path to that that leaves Python
> "easily extended".

All of the differences matter! Inconsistency is a problem in and of
itself.

> But not a __name__.

They really do have __name__s. Try it. type("").__name__

> 
> > They are not (yet) callable but I
> > cannot think of a circumstance in which that would matter.
> 
> Take a look at copy.py.

copy.py only expects the type object to be callable WHEN there is a
getinitargs method. Types won't have this method so it won't use the
class callably. Plus, the whole section only gets run for objects of
type InstanceType.

The important point is that it is not useful to know that __class__ is
callable without knowing the arguments it takes. __class__ is much more
often used as a unique identifier for pointer equality and/or for the
__name__. In looking through the standard library, I can only see places
that the code would improve if __class__ were available for extension
objects.

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