prog.py

import gc
import threading

def thread_main():
    return 1

def work():
    ts = [threading.Thread(target=thread_main) for _ in range(3)]
    for t in ts:
        t.start()
    for t in ts:
        t.join()

def gc_collect():
    for i in range(3):
        gc.collect()

gc_collect()
n = []
meths = [{} for _ in range(3)]
for i in range(3):
    work()
    gc_collect()
    objs = gc.get_objects()
    n.append(len(objs))
    for obj in objs:
        if str(type(obj)) == "<class 'method'>":
            meths[i][id(obj)] = obj
    del objs

import pprint
print("diff 0-1:")
pprint.pprint([meths[1][k] for k in set(meths[1]) - set(meths[0])])
print("diff 1-2:")
pprint.pprint([meths[2][k] for k in set(meths[2]) - set(meths[1])])
print(f"gc.garbage has {len(gc.garbage)} things")
assert (
    n[0] == n[1] == n[2]
), f"objects leaked: {n[1] - n[0]}, {n[2] - n[1]}"