问题描述
如何使用 python 的多处理池处理 KeyboardInterrupt 事件?这是一个简单的例子:
How can I handle KeyboardInterrupt events with python's multiprocessing Pools? Here is a simple example:
from multiprocessing import Pool from time import sleep from sys import exit def slowly_square(i): sleep(1) return i*i def go(): pool = Pool(8) try: results = pool.map(slowly_square, range(40)) except KeyboardInterrupt: # **** THIS PART NEVER EXECUTES. **** pool.terminate() print "You cancelled the program!" sys.exit(1) print " Finally, here are the results: ", results if __name__ == "__main__": go()
在运行上面的代码时,当我按下 ^C 时,KeyboardInterrupt 会被引发,但该进程会在此时挂起,我必须在外部将其杀死.
When running the code above, the KeyboardInterrupt gets raised when I press ^C, but the process simply hangs at that point and I have to kill it externally.
我希望能够随时按 ^C 并让所有进程正常退出.
I want to be able to press ^C at any time and cause all of the processes to exit gracefully.
推荐答案
这是一个 Python 错误.在 threading.Condition.wait() 中等待条件时,永远不会发送 KeyboardInterrupt.再现:
This is a Python bug. When waiting for a condition in threading.Condition.wait(), KeyboardInterrupt is never sent. Repro:
import threading cond = threading.Condition(threading.Lock()) cond.acquire() cond.wait(None) print "done"
KeyboardInterrupt 异常在 wait() 返回之前不会被传递,并且它永远不会返回,因此中断永远不会发生.KeyboardInterrupt 几乎肯定会中断条件等待.
The KeyboardInterrupt exception won't be delivered until wait() returns, and it never returns, so the interrupt never happens. KeyboardInterrupt should almost certainly interrupt a condition wait.
请注意,如果指定了超时,则不会发生这种情况;cond.wait(1) 将立即收到中断.因此,一种解决方法是指定超时.为此,请替换
Note that this doesn't happen if a timeout is specified; cond.wait(1) will receive the interrupt immediately. So, a workaround is to specify a timeout. To do that, replace
results = pool.map(slowly_square, range(40))
与
results = pool.map_async(slowly_square, range(40)).get(9999999)
或类似的.