On 13 September 2013 07:29, Tim Delaney <timothy.c.dela...@gmail.com> wrote:
> > In this case though, there are two pieces of information: > > 1. A canonical key (which may or may not equal the original key); > > 2. The original key. > > It seems to me then that TransformDict is a specialised case of > CanonicalDict, where the canonical key is defined to be the first key > inserted. It would in fact be possible (though inefficient) to implement > that using a canonicalising callable that maintained state - something like > (untested): > > class OriginalKeys: > def __init__(self):: > self.keys = CanonicalDict(str.lower) > > def __call__(self, key): > return self.keys.setdefault(key, key) > > class OriginalKeyDict(CanonicalDict): > def __init__(self):: > super().__init__(OriginalKeys()) > Bah - got myself mixed up with original key and case preserving there ... try this: class OriginalKeys: def __init__(self, func):: self.keys = CanonicalDict(func) def __call__(self, key): return self.keys.setdefault(key, key) class OriginalKeyDict(CanonicalDict): def __init__(self, func):: super().__init__(OriginalKeys(func)) class IdentityDict(OriginalKeyDict): def __init__(self): super().__init__(id) class CasePreservingDict(OriginalKeyDict): def __init__(self): super().__init__(str.lower) Tim Delaney
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