gistfile1.py

class Foo(object):
    @property
    def foo(self):
        """This foo is not implemented"""
        raise NotImplementedError

    def do_thing(self):
        print self.foo

class Bar(Foo):
    foo = "bar"

bar = Bar()
bar.do_thing() #Fine

foo = Foo()
foo.do_thing() #Boom