"""How to create a custom mappable container (dictionary-like) type in Python."""
 
from UserDict import DictMixin
 
class MyDict(DictMixin):
    # MyDict only needs to implement getitem, setitem, delitem and keys (at a 
    # minimum) and UserDict will provide the rest of the standard dictionary
    # methods based on these four.
    #
    # getitem and delitem should raise KeyError if no item exists for the given
    # key. getitem, setitem and delitem should raise TypeError if the given key
    # is of the wrong type.
 
    def __getitem__(self, key):
        ....
 
    def __setitem__(self, key, item):
        ....
 
    def __delitem__(self, key):
        ....
 
    def keys(self):
        ....
 
# You can now use your class as if it was a dict, using the standard container 
# operators and dictionary methods.
 
d = MyDict()
d[key] = value
d.get(key)
d.clear()
etc.