如何同时运行两个线程并等待结果

Question

I would like to run from my python code two instances of one program as different threads. And after both of them finishes I would like to do some other stuff.

Lets say I have code like that:

import logging
import threading
import time


def thread_function(name):
    logging.info("Thread %s: starting ", name)
    time.sleep(2)
    logging.info("Thread %s: finishing ", name)


def main():
    format = "%(asctime)s: %(message)s"
    logging.basicConfig(format=format, level=logging.INFO, datefmt="%H:%M:%S")

    logging.info("Main: before creating thread")
    x = threading.Thread(target=thread_function, args=(1,))
    logging.info("Main: before running thread")
    x.start()
    logging.info("Main: wait for the thread to finish")
    logging.info("Main: all done")


if __name__ == "__main__":
    main()

This code prints Main: all done before the two threads finish. But I would like to wait until they are finished and than print all Done . Any ideas how to solve it?

Answer 1

You can use thread.join() to wait for a Thread to finish.

import logging
import threading
import time


def thread_function(name):
    logging.info("Thread %s: starting ", name)
    time.sleep(2)
    logging.info("Thread %s: finishing ", name)


def main():
    format = "%(asctime)s: %(message)s"
    logging.basicConfig(format=format, level=logging.INFO, datefmt="%H:%M:%S")

    logging.info("Main: before creating thread")
    x = threading.Thread(target=thread_function, args=(1,))
    logging.info("Main: before running thread")
    x.start()
    logging.info("Main: wait for the thread to finish")
    x.join()
    logging.info("Main: all done")


if __name__ == "__main__":
    main()

Answer 2

join(timeout=None)¶

Wait until the thread terminates. This blocks the calling thread until the thread whose join() method is called terminates – either normally or through an unhandled exception – or until the optional timeout occurs.