Method test_pickle_slots

Lib/test/test_descr.py:5531–5596

(self)

    @support.thread_unsafe
    def test_pickle_slots(self):
        # Tests pickling of classes with __slots__.

        # Pickling of classes with __slots__ but without __getstate__ should
        # fail (if using protocol 0 or 1)
        global C
        class C:
            __slots__ = ['a']
        with self.assertRaises(TypeError):
            pickle.dumps(C(), 0)

        global D
        class D(C):
            pass
        with self.assertRaises(TypeError):
            pickle.dumps(D(), 0)

        class C:
            "A class with __getstate__ and __setstate__ implemented."
            __slots__ = ['a']
            def __getstate__(self):
                state = getattr(self, '__dict__', {}).copy()
                for cls in type(self).__mro__:
                    for slot in cls.__dict__.get('__slots__', ()):
                        try:
                            state[slot] = getattr(self, slot)
                        except AttributeError:
                            pass
                return state
            def __setstate__(self, state):
                for k, v in state.items():
                    setattr(self, k, v)
            def __repr__(self):
                return "%s()<%r>" % (type(self).__name__, self.__getstate__())

        class D(C):
            "A subclass of a class with slots."
            pass

        global E
        class E(C):
            "A subclass with an extra slot."
            __slots__ = ['b']

        # Now it should work
        for pickle_copier in self._generate_pickle_copiers():
            with self.subTest(pickle_copier=pickle_copier):
                x = C()
                y = pickle_copier.copy(x)
                self._assert_is_copy(x, y)

                x.a = 42
                y = pickle_copier.copy(x)
                self._assert_is_copy(x, y)

                x = D()
                x.a = 42
                x.b = 100