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...) Eli
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