import weakref

class WeakList(list):

    def __init__(self, items = ()):
        super(WeakList, self).__init__([weakref.ref(i, self.remove) for i in items])

    def __contains__(self, item):
        return super(WeakList, self).__contains__(weakref.ref(item))

    def __getitem__(self, index):
        if isinstance(index, slice):
            return [i() for i in super(WeakList, self).__getitem__(index)]
        else:
            return super(WeakList, self).__getitem__(index)()

    def __setitem__(self, index, item):
        if isinstance(index, slice):
            item = [weakref.ref(i, self.remove) for i in item]
        else:
            item = weakref.ref(item, self.remove)

        return super(WeakList, self).__setitem__(index, item)

    def __iter__(self):
        for i in list(super(WeakList, self).__iter__()):
            yield i()

    def remove(self, item):
        if isinstance(item, weakref.ReferenceType):
            super(WeakList, self).remove(item)
        else:
            super(WeakList, self).remove(weakref.ref(item))

    def append(self, item):
        return super(WeakList, self).append(weakref.ref(item, self.remove))


# write some test code:
class Dummy():
    pass
    
a = Dummy()
b = Dummy()

l = WeakList()
l.append(a)
l.append(b)

print('a:', a)
print('b:', b)

print('l should contain weak references:', l)
print('a copy of l gets you real list:', [i for i in l])

print('casting l with list gets you atual objects', list(l))

print('casting l to tuple gets you... weak refs instead:', tuple(l))