[Python-3000] pep 3124 plans

Tue Jul 31 11:40:12 CEST 2007

Phillip J. Eby wrote:
> In other words, a class' metaclass has to be a derivative of all its 
> bases' metaclasses; ISTM that a __prepare__ namespace needs to be a 
> derivative in some sense of all its bases' __prepare__ results. This 
> probably isn't enforceable, but the pattern should be documented such 
> that e.g. the overloading metaclass' __prepare__ would return a 
> mapping that delegates operations to the mapping returned by its 
> super()'s __prepare__, and the actual class creation would be 
> similarly chained. PEP 3115 probably needs a section to explain 
> these issues and recommend best practices for implementing 
> __prepare__ and class creation on that basis. I'll write something 
> up after I've thought this through some more.

A variant of the metaclass rule specific to __prepare__ might look 
something like:
 A class's metaclass providing the __prepare__ method must be a 
subclass of all of the class's base classes providing __prepare__ methods.
Cheers,
Nick.
-- 
Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia
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