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

[Antoine Pitrou]

Le Wed, 11 Sep 2013 07:48:56 -0700,
Ethan Furman <ethan at stoneleaf.us> a écrit :
> On 09/11/2013 06:58 AM, Victor Stinner wrote:
> >
> > The os.environ mapping uses a subclass of MutableMapping which
> > accepts 4 functions: encoder/decoder for the key and encoder/decoder
> > for the value. Such type is even more generic. transformdict cannot
> > replace os._Environ.
> 
> True, it's more generic -- but is it used more often?  Or often
> enough to have those four functions be part of transformdict instead
> of just the one encodekey function?  (I mean the idea of os._Environ,
> not that specific implementation.)
> 
> Personally, I wouldn't mind having all four; for one thing, the name
> 'transformdict' would then be entirely appropriate.  ;)

The key decoder function is quite useless since the original key is
retained. As for the value encoder/decoder, I don't really see the
point: just store whichever value you want to retrieve later. The main
point of transformdict is that the *lookup* is done using a different
key than the user-provided key.

Regards

Antoine.