Python：如何让程序等待函数或方法完成

程序经常需要等待函数完成其工作。有时恰恰相反：主程序不需要等待。 我举了一个简单的例子。有四个按钮。单击每个将调用相同的calculate()函数。唯一的区别是函数的调用方式。

1. “直接打电话”

使用队列：每个线程完成后将结果放入队列中，然后您只需读取适当数量的结果并忽略其余部分：

#!python3.3
import queue    # For Python 2.x use 'import Queue as queue'
import threading, time, random

def func(id, result_queue):
    print("Thread", id)
    time.sleep(random.random() * 5)
    result_queue.put((id, 'done'))

def main():
    q = queue.Queue()
    threads = [ threading.Thread(target=func, args=(i, q)) for i in range(5) ]
    for th in threads:
        th.daemon = True
        th.start()

    result1 = q.get()
    result2 = q.get()

    print("Second result: {}".format(result2))

if __name__=='__main__':
    main()

Queue.get() 的文档（没有参数，它相当于 Queue.get(True, None)：

    Queue.get([block[, timeout]])

Remove and return an item from the queue. If optional args block is true and timeout is None (the default), block if necessary until an item is available. If timeout is a positive number, it blocks at most timeout seconds and raises the Empty exception if no item was available within that time. Otherwise (block is false), return an item if one is immediately available, else raise the Empty exception (timeout is ignored in that case).

如何在Python中等待第一个线程完成 https://stackoverflow.com/questions/17564804/in-python-how-to-wait-until-only-the-first-thread-is-finished

您也可以使用 .join() 方法。python 线程中 join() 有什么用 https://stackoverflow.com/questions/15085348/what-is-the-use-of-join-in-python-threading