Enable pickling on Python classes that uses __slots__

slots_pickling_mixin.py

class SlotsPicklingMixin(object):
    # otherwise, subclasses will still have `__dict__`
    __slots__ = ()

    def __init__(self):
        assert hasattr(self, '__slots__')

    def __getstate__(self):
        all_slots = itertools.chain.from_iterable(
            getattr(t, '__slots__', ()) for t in type(self).__mro__)
        state = {attr: getattr(self, attr) for attr in all_slots
                 if hasattr(self, attr)}
        return state

    def __setstate__(self, state):
        print "Setting", self.__class__.__name__
        for k, v in state.iteritems():
            setattr(self, k, v)


class SampleA(SlotsPicklingMixin):
    __slots__ = ('my_a',)

    def __init__(self, my_a):
        super(SampleA, self).__init__()
        self.my_a = my_a


class SampleB(SampleA):
    __slots__ = ('my_b',)

    def __init__(self, my_b, *args, **kwargs):
        super(SampleB, self).__init__(*args, **kwargs)
        self.my_b = my_b

If you try to pickle a SampleB object, wont you loose the 'my_a' attribute? I thinks so

@huitredelombre you are right! not sure how it happened :) fixed!