test_weakref.py 文件源码

def check_len_race(self, dict_type, cons):
        # Extended sanity checks for len() in the face of cyclic collection
        self.addCleanup(gc.set_threshold, *gc.get_threshold())
        for th in range(1, 100):
            N = 20
            gc.collect(0)
            gc.set_threshold(th, th, th)
            items = [RefCycle() for i in range(N)]
            dct = dict_type(cons(o) for o in items)
            del items
            # All items will be collected at next garbage collection pass
            it = dct.iteritems()
            try:
                next(it)
            except StopIteration:
                pass
            n1 = len(dct)
            del it
            n2 = len(dct)
            self.assertGreaterEqual(n1, 0)
            self.assertLessEqual(n1, N)
            self.assertGreaterEqual(n2, 0)
            self.assertLessEqual(n2, n1)