Python: using __getitem__ in a class and using in to find that item

Question

I do the following

class dumb(object):
    def __init__(self):
        self.g = {}
    def __getitem__(self,key): return self.g[key] if key in self.g else None
    def __setitem__(self,key,val):
        self.g[key] = val


te = dumb()

te[1]=2

te[1]
Out[4]: 2

1 in te

and it hangs..

So if I want to search something like this, how do i do that? Please don't tell me to subclass class dictionary.

Thanks in advance!

Possible relevant question asked here: What does __contains__ do, what can call __contains__ function

Answer 1

For in to work correctly, you need to override __contains__():

class dumb(object):
    ...
    def __contains__(self, key):
        return key in self.g

By the way,

self.g[key] if key in self.g else None

can be more succinctly written as

self.g.get(key)

Answer 2

In order to be able to do something like:

    1 in te

you have to define __contains__ method

    class dumb(object):
        def __init__(self):
            self.g = {}
        def __getitem__(self,key): return self.g[key] if key in self.g else None

        def __setitem__(self,key,val):
            self.g[key] = val

        def __contains__(self, item):
            return item in self.g