On 7/13/07, Talin <[EMAIL PROTECTED]> wrote: > Thomas Heller wrote: > > playing a little with py3k... > > > > pep3115 mentions that "__prepare__ returns a dictionary-like object > > which is used to store the class member definitions during evaluation > > of the class body." > > > > It does not mention whether this dict-like object is used afterwards > > as the class-dictionary of the created class or not (when the __new__ > > method of the metaclass is called). > > The intention is that it's up to the metaclass to decide. I suspect that > most metaclasses won't want to use the dict-like object as the class > dict, for two reasons: > > 1) The behavior of assigning to the class dict after class creation is > likely to be different than the behavior of assignment during class > creation. In particular, a typical 'dict-like' object is likely to be > slower than a dict (it has more work to do, after all), and you don't > want that slowness around once your class is finished initializing. > > 2) A 'dict-like' object doesn't have to support all of the methods of a > real dict, wherease a class dict does. So your dict-like wrapper can be > relatively simple.
The object returned by __prepare__() actually *is* incorporated into the class object, unless the metaclass' __new__() passes something else to type.__new__(). However this isn't obvious when you ask for the class' __dict__ attribute: you always get a dict proxy. -- --Guido van Rossum (home page: http://www.python.org/~guido/) _______________________________________________ Python-3000 mailing list Python-3000@python.org http://mail.python.org/mailman/listinfo/python-3000 Unsubscribe: http://mail.python.org/mailman/options/python-3000/archive%40mail-archive.com
