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. -eric > > On Sat, May 23, 2015 at 7:38 PM, Nick Coghlan <ncogh...@gmail.com> wrote: >> >> On 24 May 2015 at 12:04, Nick Coghlan <ncogh...@gmail.com> wrote: >> > On 24 May 2015 at 11:15, Eric Snow <ericsnowcurren...@gmail.com> wrote: >> >> tl;dr Are there any objections to making making the default >> >> cls.__prepare__ return OrderedDict instead of dict (and preserve that >> >> order in a list on the class)? >> >> >> >> A couple years ago [1][2] I proposed making class definition >> >> namespaces use OrderedDict by default. Said Guido [3]: >> >> >> >> I'm fine with doing this by default for a class namespace; the type of >> >> cls.__dict__ is already a non-dict (it's a proxy) and it's unlikely to >> >> have 100,000 entries. >> >> >> >> It turns out making cls.__dict__ an OrderedDict isn't reasonably >> >> tractable (due to the concrete API v. subclasses), but really that >> >> isn't what I was looking for anyway. >> >> >> >> Regardless, since it's been a while I just want to run the proposal by >> >> the group again. I'm hopeful about landing my C implementation of >> >> OrderedDict [4] in the next few days. Also, I have a patch up [5] >> >> that implements using OrderedDict for class definitions. So mostly I >> >> just want to double check that I'm still good to go. >> > >> > While it isn't controversial (since you already have the +1 from >> > Guido), it's worth writing up the change as a PEP for 3.6 anyway, >> > since that then provides clearer guidance to alternate implementations >> > that they're going to need to change the way their class namespace >> > evaluation works for 3.6. >> >> Eric clarified for me that Larry was considering granting a feature >> freeze exemption to defer landing this to beta 2 while Eric tracked >> down a segfault bug in the current patch that provides a C >> implementation of OrderedDict. That sounds like a nicer approach than >> what I did for PEP 489 (where I checked in an initial version that I >> knew still had a refleak bug in it), so +1 from me for going down that >> path. >> >> A top level section in the What's New would cover my concerns >> regarding making sure folks are suitably aware of the change (as I >> believe leaving it out of the original 2.6 What's New document was the >> real problem with making people aware of the addition of zip archive >> and directory execution support). >> >> 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/guido%40python.org > > > > > -- > --Guido van Rossum (python.org/~guido)
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