2011/5/5 Giuseppe Ottaviano <giuott@gmail.com>:

...

The only thing I would add is obj.copy(), to ensure that the original dictionary is unchanged.

class using(object):    def __init__(self, obj):        self._wrappee = obj.copy()

My example was just a proof of concept, there are many other things that may need to be taken care of (for example, non-callable attributes). BTW, the copy should be done outside. If the object is copied, I'd say "using" is a poor choice of name for the proxy.

You're right, I would need to do more work to get it to mimic the underlying object. I think I will stick with Oleg's suggestion to subclass dict for now; it's great for unit tests. Thanks for the idea, though. class ReplaceableDict(dict): def replace(self, **kwargs): 'Works for replacing string-based keys' return dict(self.items() + kwargs.items())