[Python-Dev] RE: Python-Dev digest, Vol 1 #1324 - 16 msgs

[Donald Beaudry]

"Thomas Heller" <thomas.heller@ion-tof.com> wrote,
> Donald Beaudry's objectmodule uses the metaclass hook to provide
> class methods. I like the resulting syntax very much:

Thank you.  I like it too, especially because MyClass.__class__
returns what *I* would expect ;) and the source reflects that too.

> If I understand correctly (objectmodule does not run under 1.5.2 or
> later), an instance of __class__ will become the metaclass of
> Object, and __class__'s methods will become class methods of Object.

That's correct.  I currently use objectmodule on 1.5.2.  I would not
be surprised if it doesnt work on newer versions though as I have
never tried it there.  Perhaps you found an out-of-date version, or
perhaps I never sent out a newer version.  Regardless, I'd be happy to
get you a version that works with 1.5.2 (or upload one somewhere for
more public consumption)

> I've played a little bit with metaclasses in pure python (it is
> faster this way), and have an implementation with the same syntax
> where __class__ is never instantiated, and simply acts as a function
> container.

Ah but with the object module, it does get instantiated.  In fact,
__class__ is derived (implicitly) from the __class__ of the containing
base class. Inheritance works as expected.

> Addendum: Additionaly to class methods, I would like to
> have 'magic' class methods, maybe named __class_init__
> and __class_getattr__. Easy to guess what they should do...

Objectmodule provides for that as well.  Just define __init__,
__getattr__, etc., inside the __class__ definition.  There is even and
__new__ which is responsible for controling the "memory allocation" of
instances.  This is useful for, amoung other things, singletons.

> > Hmmm... might write a PEP on that!
> > 
> Me too.

...gone are the days when a simple email to Guido was all it took to
get a proposal going ;)

--
Donald Beaudry                                     Ab Initio Software Corp.
                                                   201 Spring Street
donb@init.com                                      Lexington, MA 02421
                  ...So much code, so little time...