Caseinsensitive Dict lookup

class CaseInsensitiveDict(dict):
    def __init__(self, *args, **kwargs):
        self.keystore = {}
        d = dict(*args, **kwargs)
        for k in d.keys():
            self.keystore[self._get_lower(k)] = k
        return super(CaseInsensitiveDict, self).__init__(*args, **kwargs)
    def __setitem__(self, k, v):
        if hasattr(self,'keystore'):
            self.keystore[self._get_lower(k)] = k
        return super(CaseInsensitiveDict, self).__setitem__(k, v)
    def __getitem__(self, k):
        if hasattr(self,'keystore') and self._get_lower(k) in self.keystore:
            k = self.keystore[self._get_lower(k)]
        return super(CaseInsensitiveDict, self).__getitem__(k)

    @staticmethod
    def _get_lower(k):
        if isinstance(k, str):
            return k.lower()
        else:
            return k

This one seems to do the trick at last.

This is based on the logic that for every key in the dictionary (you create for
you want a Caseinsensitive Dict lookup), store the key in the lower value in
the keystore.

When you retreive a item from the Dict, let your request be in any case, but
lower it and then lookup the actual key as it was stored in the keystore and
then retrieve the value using that key.

As the __init__, __setitem__, __getitem__ methods use the super() call to dict,
and using the *same* key and the value passed to the normal dictionary, this
class with an internal keystore would behave as unsuspecting as possible.

Devised this way after a good number of trials.
Lesson to myself:

Study the concepts, try the code before you look for examples in the web,
otherwise you tend to get influenced by examples. Sometimes it might be
helpful, that would only serve as learning. You might want to get back to
implement in the wayyou best understand.

During this patch workout, got to know mixins, decorators, staticmethod,
classmethod, dict more.

There are still couple of tests failing with
Issue2275(http://bugs.python.org/issue2275) , hopefully I would have ironed
them out by today.