非阻塞方式来确定线程是否完成？

Question

我有以下代码：

import threading
import time

class TestWorker (threading.Thread):
    def __init__(self, threadID, name):
        threading.Thread.__init__(self)
        self.threadID = threadID
        self.name = name

    def run(self):
        print "Starting " + self.name
        time.sleep(20)
        print "Exiting " + self.name
        # how do I let the calling thread know it's done?

class TestMain:
    def __init__(self):
        pass

    def do_work(self):
        thread = TestWorker(1, "Thread-1")
        thread.start()

    def do_something_else(self):
        print "Something else"

    def on_work_done(self):
        print "work done"

如何让主线程知道已经TestWorker完成（调用），而不阻塞on_work_done()调用？do_something_else()thread.join()

Answer 1

您可以为线程实例提供一个可选的回调函数，以便在其完成时调用。
注意我添加了一个Lock来防止并发打印（它会阻塞）。

print_lock = threading.Lock()  # Prevent threads from printing at same time.

class TestWorker(threading.Thread):
    def __init__(self, threadID, name, callback=lambda: None):
        threading.Thread.__init__(self)
        self.threadID = threadID
        self.name = name
        self.callback = callback

    def run(self):
        with print_lock:
            print("Starting " + self.name)
        time.sleep(3)
        with print_lock:
            print("Exiting " + self.name)
        self.callback()

class TestMain:
    def __init__(self):
        self.work_done = False

    def do_work(self):
        thread = TestWorker(1, "Thread-1", self.on_work_done)
        thread.start()

    def do_something_else(self):
        with print_lock:
            print("Something else")

    def on_work_done(self):
        with print_lock:
            print("work done")
        self.work_done = True

main = TestMain()
main.do_work()
while not main.work_done:
    main.do_something_else()
    time.sleep(.5)  # do other stuff...

print('Done')

输出：

print_lock = threading.Lock()  # Prevent threads from printing at same time.

class TestWorker(threading.Thread):
    def __init__(self, threadID, name, callback=lambda: None):
        threading.Thread.__init__(self)
        self.threadID = threadID
        self.name = name
        self.callback = callback

    def run(self):
        with print_lock:
            print("Starting " + self.name)
        time.sleep(3)
        with print_lock:
            print("Exiting " + self.name)
        self.callback()

class TestMain:
    def __init__(self):
        self.work_done = False

    def do_work(self):
        thread = TestWorker(1, "Thread-1", self.on_work_done)
        thread.start()

    def do_something_else(self):
        with print_lock:
            print("Something else")

    def on_work_done(self):
        with print_lock:
            print("work done")
        self.work_done = True

main = TestMain()
main.do_work()
while not main.work_done:
    main.do_something_else()
    time.sleep(.5)  # do other stuff...

print('Done')