[Python-Dev] Add a "transformdict" to collections

[Ethan Furman]

On 09/11/2013 02:39 PM, Tim Delaney wrote:
>
> I would think that retrieving the keys from the dict would return the transformed keys (I'd
> call them canonical keys).

The more I think about this the more I agree.  A canonicaldict with a key function that simply stored the transformed 
key and it's value would seem to be a lot simpler:

   - no need to store a separate "presentation" key
   - no confusion about which of the first key/last key seen is stored
   - no mistakes with the "first" key not being added before real data
     and getting the presentation key wrong

Further, in order to store the non-canonical keys a separate list must be kept of the keys to preseed the canonicaldict; 
if we store the canonical keys a separate list must be kept for presentation purposes -- so worst case scenario we're 
keeping the same amount of information and best-case scenario the presentation of the keys doesn't matter and we just 
saved ourselves an extra data structure.

--
~Ethan~