一段时间后终止线程的最 Pythonic 方法

我想在线程中运行一个进程（它正在迭代一个大型数据库表）。当线程运行时，我只想让程序等待。如果该线程花费的时间超过 30 秒，我想终止该线程并执行其他操作。通过终止线程，我的意思是我希望它停止活动并优雅地释放资源。

我认为最好的方法是通过Thread()'s join(delay) and is_alive()功能，以及Event。使用join(delay)我可以让我的程序等待 30 秒让线程完成，并使用is_alive()函数我可以确定线程是否已完成其工作。如果它尚未完成其工作，则会设置事件，并且线程知道此时停止工作。

这种方法是否有效，这是解决我的问题陈述的最Pythonic的方法吗？

这是一些示例代码：

import threading
import time

# The worker loops for about 1 minute adding numbers to a set
# unless the event is set, at which point it breaks the loop and terminates
def worker(e):
    data = set()
    for i in range(60):
        data.add(i)
        if not e.isSet():
            print "foo"
            time.sleep(1)
        else:
            print "bar"
            break

e = threading.Event()
t = threading.Thread(target=worker, args=(e,))
t.start()

# wait 30 seconds for the thread to finish its work
t.join(30)
if t.is_alive():
    print "thread is not done, setting event to kill thread."
    e.set()
else:
    print "thread has already finished."

在这种情况下使用事件作为信号机制就可以很好地工作，并且 实际上是推荐的线程模块文档 https://docs.python.org/2/library/threading.html#module-threading.

如果您希望线程正常停止，请将它们设置为非守护线程并使用 合适的信号机制，例如Event.

当验证线程终止时，超时几乎总是会带来空间 错误。因此，在使用时.join()初始超时 触发事件的决定很好，最终验证应该使用.join()没有超时。

# wait 30 seconds for the thread to finish its work
t.join(30)
if t.is_alive():
    print "thread is not done, setting event to kill thread."
    e.set()
    # The thread can still be running at this point. For example, if the 
    # thread's call to isSet() returns right before this call to set(), then
    # the thread will still perform the full 1 second sleep and the rest of 
    # the loop before finally stopping.
else:
    print "thread has already finished."

# Thread can still be alive at this point. Do another join without a timeout 
# to verify thread shutdown.
t.join()

这可以简化为这样：

# Wait for at most 30 seconds for the thread to complete.
t.join(30)

# Always signal the event. Whether the thread has already finished or not, 
# the result will be the same.
e.set()

# Now join without a timeout knowing that the thread is either already 
# finished or will finish "soon."
t.join()