[Python-Dev] PEP 455: TransformDict

[Ethan Furman]

On 09/14/2013 03:27 AM, Antoine Pitrou wrote:
> On Fri, 13 Sep 2013 21:59:11 -0700
> Ethan Furman <ethan at stoneleaf.us> wrote:
>>
>>> I mean - given no function to retrieve the canonical key,
>>> one would have to resort to:
>>>
>>> my_key = data.__transform__(given_key)
>>> for key, value in data.items():
>>>       if data.__transform__(key) == my_key:
>>>           ....
>>
>> Which is exactly why I, and others, would like to have the transform function easily available.  Besides being able to
>> use it to get a canonical key, one could use it to get the function itself.  Yay, introspection!
>
> Well, no, you misunderstand :) The transform function takes an
> original key (perhaps "canonical") and returns the transformed key, it
> can't do the reverse which is what getitem() does.  i.e.:

Argh, of course you are right.

Still, I think it would be useful to expose the transform function.  Any good reason not to?

--
~Ethan~