python的多处理池的键盘中断
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.
解决方案
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.
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