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

[Paul Moore]

On 10 September 2013 13:00, Nick Coghlan <ncoghlan at gmail.com> wrote:
> Is this just syntactic sugar for recursive lookup of a transformed version
> in __missing__? Or a way of supplying a custom "key" function to a
> dictionary?

Not quite, because the dict should preserve the originally entered key.

>>> td['FOO'] = 42
>>> td['bar'] = 1
>>> td['foo']
42
>>> td['BAR']
1
>>> list(td.keys())
['FOO', 'bar']

This actually prompts the question, what should the following produce:

>>> td['FOO'] = 42
>>> td['foo'] = 32
>>> list(td.keys())

['FOO'] or ['foo']? Both answers are justifiable. Both are possibly
even useful depending on context...

Paul