如何将数据发送到正在运行的 python 线程？

Question

我有一个在我的应用程序的单独线程中运行的类。我可以同时运行多个线程，这些线程是守护进程。一段时间后，这些线程中有一些需要接收和处理消息。我该怎么做？

我的代码示例如下所示：

import threading
import time 

class MyThread(threading.Thread):
    def __init__(self, args=(), kwargs=None):
        threading.Thread.__init__(self, args=(), kwargs=None)
        self.daemon = True
        self.receive_messages = args[0]

    def run(self):
        print threading.currentThread().getName(), self.receive_messages

    def do_thing_with_message(self, message):
        if self.receive_messages:
            print threading.currentThread().getName(), "Received %s".format(message)

if __name__ == '__main__':
    threads = []
    for t in range(10):
        threads.append( MyThread(args=(t % 2 == 0,)))
        threads[t].start()
        time.sleep(0.1)

    for t in threads:
        t.do_thing_with_message("Print this!")

这个输出：

Thread-1 True
Thread-2 False
Thread-3 True
Thread-4 False
Thread-5 True
Thread-6 False
Thread-7 True
Thread-8 False
Thread-9 True
Thread-10 False
MainThread Received %s
MainThread Received %s
MainThread Received %s
MainThread Received %s
MainThread Received %s

但是，我希望最后五行与MainThread 无关，而不是%s，我希望它与Print this! 相关，如下所示：

Thread-1 True
Thread-2 False
Thread-3 True
Thread-4 False
Thread-5 True
Thread-6 False
Thread-7 True
Thread-8 False
Thread-9 True
Thread-10 False
Thread-1 Received Print this!
Thread-3 Received Print this!
Thread-5 Received Print this!
Thread-7 Received Print this!
Thread-9 Received Print this!

我怎样才能正确地向正在运行的线程发送这样的消息？

附录：

如果我在Print this! 块之后有这个块，并利用@dano 的代码解决上述问题，它似乎没有响应这些新消息。

for t in threads:
    t.queue.put("Print this again!")
    time.sleep(0.1)

在这种情况下，我希望我的输出的结尾看起来像这样

Thread-1 Received Print this!
Thread-3 Received Print this!
Thread-5 Received Print this!
Thread-7 Received Print this!
Thread-9 Received Print this!
Thread-1 Received Print this again!
Thread-3 Received Print this again!
Thread-5 Received Print this again!
Thread-7 Received Print this again!
Thread-9 Received Print this again!

Answer 1

您可以为此使用 Queue.Queue（或 Python 3 中的 queue.Queue）：

import threading
import time 
from Queue import Queue

print_lock = threading.Lock()

class MyThread(threading.Thread):
    def __init__(self, queue, args=(), kwargs=None):
        threading.Thread.__init__(self, args=(), kwargs=None)
        self.queue = queue
        self.daemon = True
        self.receive_messages = args[0]

    def run(self):
        print threading.currentThread().getName(), self.receive_messages
        val = self.queue.get()
        self.do_thing_with_message(val)

    def do_thing_with_message(self, message):
        if self.receive_messages:
            with print_lock:
                print threading.currentThread().getName(), "Received {}".format(message)

if __name__ == '__main__':
    threads = []
    for t in range(10):
        q = Queue()
        threads.append(MyThread(q, args=(t % 2 == 0,)))
        threads[t].start()
        time.sleep(0.1)

    for t in threads:
        t.queue.put("Print this!")

    for t in threads:
        t.join()

我们将Queue 实例传递给每个线程，并使用queue.put 将我们的消息发送到Thread。我们等待消息到达run 方法，它是Thread 对象的一部分，实际上在单独的执行线程中运行。收到消息后，我们调用do_thing_with_message，它将在同一个后台线程中运行。

我还在代码中添加了threading.Lock，这样打印到标准输出的内容就不会混淆。

编辑：

如果您希望能够向线程传递多条消息，只需使用循环：

def run(self):
    print threading.currentThread().getName(), self.receive_messages
    while True:
        val = self.queue.get()
        if val is None:   # If you send `None`, the thread will exit.
            return
        self.do_thing_with_message(val)