[Python-3000] PEP 3124 - Overloading, Generic Functions, Interfaces, etc.

Jim Jewett jimjjewett at gmail.com
Tue May 1 16:11:26 CEST 2007

On 4/30/07, Phillip J. Eby <pje at telecommunity.com> wrote:
> At 07:29 PM 4/30/2007 -0400, Jim Jewett wrote:
> >On 4/30/07, Phillip J. Eby <pje at telecommunity.com> wrote:

> >>PEP 3115, however, requires that a class' metaclass be determined
> >>*before* the class body has executed, making it impossible to use this
> >>technique for class decoration any more.

> >It doesn't say what that metaclass has to do, though.

> >Is there any reason the metaclass couldn't delegate differently
> >depending on the value of __my_magic_attribute__ ?

> Sure -- that's what I suggested in the "super(), class decorators, and PEP
> 3115" thread, but Guido voted -1 on adding such a magic attribute to PEP
> 3115.

I don't think we're understanding each other.  Why couldn't you use a
suitably fleshed-out version of:

class _ConditionalMetaclass(type):

    def __init__(cls, name, bases, dct):
        super(_ConditionalMetaclass, cls).__init__(name, bases, dct)
        hooks = [(k, v) for (k, v) in dct.items() if
        for k, v in hooks:
            cls = AfterHooksRegistry[k](cls, v)


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