.py

import gc
import random
import contextlib


class Opener:
    def __enter__(self):
        return random.randint(1, 100)

    def __exit__(self, *args):
        pass


@contextlib.contextmanager
def make_context(obj):
    print('a', len(gc.get_referrers(obj)))
    with obj as val:
        print('b', len(gc.get_referrers(obj)))
        del obj
        yield val


def test_referrers():
    opener = Opener()
    assert len(gc.get_referrers(opener)) == 0
    with make_context(opener) as val:
        assert len(gc.get_referrers(opener)) == 0
        del opener
        assert isinstance(val, int)


__name__ == '__main__' and test_referrers()