case insensitive dictionary

[John Henry]

I believe the standard dictionary should be amened to allow the use of
case insensitive keys - as an option.  I found some work done by others
to do that at:

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/283455

but the problem with that approach is that they lowercase the keys
immediately when you create the dictionary and so the true identity of
the key is lost.

Of course, I can subclass it and save a copy of the "real" key but
that's kind of messcy.

In other words:

If I have:

    pets=caselessDict()

    pets["Cat"] = 3
    pets["Dog"] = 2

I would like to see:

   pets["cat"]  prints 3
   pets["DOG"] prints 2

but

   print pets.keys()

should print:

"Cat", "Dog"

not:

"cat", "dog"