import timeimport threadingdef task_thread(counter):    print(f'线程名称：{threading.current_thread().name} 参数：{counter} 开始时间：{time.strftime("%Y-%m-%d %H:%M:%S")}')    num = counter    while num:        time.sleep(3)        num -= 1    print(f'线程名称：{threading.current_thread().name} 参数：{counter} 结束时间：{time.strftime("%Y-%m-%d %H:%M:%S")}')if __name__ == '__main__':    print(f'主线程开始时间：{time.strftime("%Y-%m-%d %H:%M:%S")}')    #初始化3个线程，传递不同的参数    t1 = threading.Thread(target=task_thread, args=(3,))    t2 = threading.Thread(target=task_thread, args=(2,))    t3 = threading.Thread(target=task_thread, args=(1,))    #开启三个线程    t1.start()    t2.start()    t3.start()    #等待运行结束    t1.join()    t2.join()    t3.join()    print(f'主线程结束时间：{time.strftime("%Y-%m-%d %H:%M:%S")}')