[Python-Dev] PEP 455: TransformDict

[Antoine Pitrou]

On Fri, 13 Sep 2013 15:32:55 -0700
Ethan Furman <ethan at stoneleaf.us> wrote:
> On 09/13/2013 02:45 PM, Antoine Pitrou wrote:
> > Serhiy Storchaka wrote:
> >>
> >> I think that's important. As OrderectDict has additional methods besides
> >> the MutableMapping API, so TransformDict should provide useful
> >> specialized methods.
> >
> > Ok, I have a better (IMO) proposal:
> >
> >      >>> d = TransformDict(str.casefold, {'Foo': 1})
> >      >>> d.getitem('foo')
> >      ('Foo', 1)
> >      >>> d.getitem('bar')
> >      Traceback (most recent call last):
> >        File "<stdin>", line 1, in <module>
> >      KeyError: 'bar'
> 
> -1
> 
> When I want the canonical key, I'm not going to care about the value; and if I do, it's easy enough to get.

But if you don't care about the value, the key is enough to get ;-)