combined_test_for_leak_weakref.py

import gc
import sys
import weakref


class C:
    def __add__(self, other):
        return NotImplemented

    def __pow__(self, other, mod=None):
        return NotImplemented

    def __eq__(self, other):
        return NotImplemented


# dead proxy
obj = type("D", (), {})()
dead = weakref.proxy(obj)
del obj
gc.collect()

# live proxy
live_obj = C()
live = weakref.proxy(live_obj)


def run(label, func):
    before = sys.gettotalrefcount()
    for _ in range(10000):
        try:
            func()
        except ReferenceError:
            pass
    after = sys.gettotalrefcount()
    print(
        f"{label}: leaked {after - before} refs (~{(after - before) // 10000}/call)"
    )


# ---- tests ----

# binary
run("binary +", lambda: live + dead)

# ternary (pow with mod)
run("ternary pow", lambda: pow(live, dead, 3))

# comparisons
run("compare ==", lambda: live == dead)