线程锁

# coding:utf-8
import os
import threading
import time
from concurrent.futures import ThreadPoolExecutor


def work(i, lock):
    lock.acquire()
    print(i)
    time.sleep(1)
    lock.release()


if __name__ == '__main__':
    lock = threading.Lock()
    t = ThreadPoolExecutor(2)
    for i in range(20):
        t.submit(work, (i, lock))

为什么这段代码运行后什么也没有输出