singleton.py

class Singleton(object):
    def __new__(cls):
        if not cls.singleton:
            cls.singleton = object.__new__(cls)
        return cls.singleton

class Foo(Singleton):
    singleton = None
    pass

class Bar(object):
    pass

f1 = Foo()
f2 = Foo()
print(f1 == f2)
print(f1)
print(f2)

b1 = Bar()
b2 = Bar()
print(b1 == b2)
print(b1)
print(b2)