class A(object):
    def __init__(self, id, string):
            self.id = id
            self.string = string

    def __eq__(self, other):
        if not hasattr(other, 'id'):
            return False
        return other.id == self.id

    def __hash__(self):
        return hash(self.id)

    def __cmp__(self, other):
        if not hasattr(other, 'id'):
            return cmp(self.id, other)
        return cmp(self.id, other.id)

a = A(1, "banana")
b = A(1, "abcdef")

assert a == b
assert hash(a) == hash(b)

assert not a < b
assert not b < a

l = [a]
assert b in l

d = {b: 1}
assert d[a] == 1