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

[Ethan Furman]

On 09/11/2013 02:39 PM, Tim Delaney wrote:
> On 12 September 2013 02:03, Ethan Furman <ethan at stoneleaf.us <mailto:ethan at stoneleaf.us>> wrote:
>
>     On 09/11/2013 08:49 AM, Victor Stinner wrote:
>
>         2013/9/11 Ethan Furman <ethan at stoneleaf.us <mailto:ethan at stoneleaf.us>>:
>
>             He isn't keeping the key unchanged (notice no white space in MAPPING), he's
>             merely providing a function that will automatically strip the whitespace
>             from key lookups.
>
>
>         transformdict keeps the key unchanged, see the first message:
>
>              >>> d = transformdict(str.lower)
>              >>> d['Foo'] = 5
>              >>> d['foo']
>              5
>              >>> d['FOO']
>              5
>              >>> list(d)
>              ['Foo']
>
> That seems backwards to me. I would think that retrieving the keys from the dict would return the transformed keys (I'd
> call them canonical keys). That way there's no question about which key is stored - it's *always* the transformed key.

At this point there is still no question: it's the first version of the key seen.  For a stupid example:

--> d = transformdict(str.lower)
--> d['ThePyramid'] = 'Game Show'
--> d['AtOnce'] = now()
--> for k, v in d.items():
...     print(k, v)

Imagine writing a function to get that capitalization right.


> In fact, I think this might get more traction if it were referred to as a canonicalising dictionary (bikeshedding, I know).

Whoa, that's way harder to spell!  ;)  Drop the 'ising', though, and I'm in.

--
~Ethan~