On 24 May 2015 at 15:53, Eric Snow <ericsnowcurren...@gmail.com> wrote: > > On May 23, 2015 10:47 PM, "Guido van Rossum" <gu...@python.org> wrote: >> >> How will __definition_order__ be set in the case where __prepare__ doesn't >> return an OrderedDict? Or where a custom metaclass's __new__ calls its >> superclass's __new__ with a plain dict? (I just wrote some code that does >> that. :-) > > I was planning on setting it to None if the order is not available. At the > moment that's just a check for OrderedDict.
Is it specifically necessary to save the order by default? Metaclasses would be able to access the ordered namespace in their __new__ method regardless, and for 3.6, I still like the __init_subclass__ hook idea proposed in PEP 487, which includes passing the original namespace to the new hook. So while I'm sold on the value of making class execution namespaces ordered by default, I'm not yet sold on the idea of *remembering* that order without opting in to doing so in the metaclass. If we leave __definition_order__ out for the time being then, for the vast majority of code, the fact that the ephemeral namespace used to evaluate the class body switched from being a basic dictionary to an ordered one would be a hidden implementation detail, rather than making all type objects a little bigger. Regards, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
