# This is not at all my actual code, but the structure is the same

import threading

def main():
    lock = threading.Lock()
    threads_ran = 0

    def thread_fn():
        nonlocal threads_ran
        with lock:
            print("threads_ran is {} on entry".format(threads_ran))
            thread_ran += 1
            print("threads_ran is {} on exit".format(threads_ran))

    threads = []
    for _ in range(10):
        threads.append(threading.Thread(target=thread_fn))
    for t in threads:
        t.start()
    for t in threads:
        t.join()

main()