Le Tue, 10 Sep 2013 07:18:41 -0700, Eli Bendersky <eli...@gmail.com> a écrit : > On Tue, Sep 10, 2013 at 5:22 AM, Antoine Pitrou <solip...@pitrou.net> > wrote: > > > Le Tue, 10 Sep 2013 22:00:37 +1000, > > Nick Coghlan <ncogh...@gmail.com> a écrit : > > > Is this just syntactic sugar for recursive lookup of a transformed > > > version in __missing__? > > > > Nope. For one, it doesn't use __missing__ at all. I think > > using __missing__ would be... missing the point, because it wouldn't > > working properly if you have e.g. X != Y such that transform(X) == Y > > and transform(Y) == X. > > > > (a simple example being transform = str.swapcase :-)) > > > > > Or a way of supplying a custom "key" function > > > to a dictionary? > > > > Probably, although I'm not entirely sure what you mean by that :-) > > > > > Any such proposal should consider how it composes with other dict > > > variants like defaultdict, OrderedDict and counter. > > > > Well, one sticking point here is that those variants don't compose > > with each other already :-) > > But, yes, I may make another proposal with composition in mind. > > > > Does anyone have an idea how to make the existing variants more > composable? It would be nice to get a better understanding of this > before we add another variant. Conceptually, composability makes a > lot of sense (what if we want this transformdict but also in > insertion order...)
AFAICT, the main problem with composability is that the implementation is less simple and it removes many opportunities for optimization. It may or may not be a problem, depending on your use cases. (I'm playing a bit with a TransformMap which is a composable version of transformdict, and it's clear the implementation is less amenable to optimization tweaks and shortcuts: in fact, I have to *add* some logic to e.g. cater with defaultdict) Regards Antoine. _______________________________________________ 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
