Python case insensitive dictionary

class CaseInsensitiveDict(dict):
    def __setitem__(self, key, value):
        key = key.lower()
        dict.__setitem__(self, key, value)

    def __getitem__(self, key):
        key = key.lower()
        return dict.__getitem__(self, key)

d = CaseInsensitiveDict()
d["Python"] = "Easy"
print d["PYTHON"]
print d["python"]

Output:

Easy
Easy