[Python-Dev] PEP 455: TransformDict

[Antoine Pitrou]

On Sat, 14 Sep 2013 09:43:13 -0700
Ethan Furman <ethan at stoneleaf.us> wrote:
> 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?

No good reason. What's the name? transform_func?

Regards

Antoine.