On 9/10/2013 2:46 PM, Antoine Pitrou wrote:
>Which reminds one - this class should obviously have a method for >retrivieng the original key value, given a matching key - > >d.canonical('foo') -> 'Foo'
I don't know. Is there any use case? (sure, it is trivially implemented)
Well, I'd expect it to simply be there. I had not thought of other usecases for the transformdict itself -
Well, it is not here for dict, set, etc.
But they don't change the keys (although numbers have different representations on occasion).
One use of transformdict might be to allow use of non-hashable items as keys, by extracting an actual key from the internals of the non-hashable item. The key may be sufficiently unique to enable use of the dict structure for lookups, but it would certainly be handy to obtain the actual item again. Without a canonical lookup feature, one would be forced to also include the key as part of the value, or some such hack.
I also thought João's example was a very practical reason to have the canonical lookup feature, by some name or another.