我认为我需要一些建议。下面是我的代码:
from multiprocessing import Pool
import time
import sys
def testing(number):
count = 0
while True:
print('Count: {}'.format(count))
count += 1
if count > number:
print('Exiting...')
sys.exit()
else:
print('Looping Over')
time.sleep(1)
if __name__ == '__main__':
with Pool(2) as p:
p.map(testing, [3, 2])
预期结果:
一旦所有子线程都退出,程序(主线程)应退出。
实际结果:
$ python3 test_exit.py
Count: 0
Looping Over
Count: 0
Looping Over
Count: 1
Looping Over
Count: 1
Looping Over
Count: 2
Looping Over
Count: 2
Exiting... <<< Exited 1st thread.
Count: 3
Exiting... <<< Exited 2nd thread.
....and it stays here as if stuck or something. It never gives control back to Shell.
预期结果:
$ python3 test_exit.py
Count: 0
Looping Over
Count: 0
Looping Over
Count: 1
Looping Over
Count: 1
Looping Over
Count: 2
Looping Over
Count: 2
Exiting...
Count: 3
Exiting...
$ <<< Note: I am expecting to be dropped back to Shell prompt
问题:
就池/地图使用而言,我的方法是否存在问题?
答案 0 :(得分:1)
一旦所有子线程都退出,程序(主线程)应退出。
testing()
(在关键循环中通过break
语句完成)来完成一个过程from multiprocessing import Pool, current_process
import time
import sys
def testing(number):
count = 0
while True:
print('Count: {}'.format(count))
count += 1
if count > number:
print('Exiting...', current_process().name)
break
else:
print('Looping Over')
time.sleep(1)
if __name__ == '__main__':
with Pool(2) as p:
p.map(testing, [3, 2])
sys.exit()
输出:
Count: 0
Looping Over
Count: 0
Looping Over
Count: 1
Looping Over
Count: 1
Looping Over
Count: 2
Looping Over
Count: 2
Exiting... ForkPoolWorker-2
Count: 3
Exiting... ForkPoolWorker-1
$
答案 1 :(得分:1)
对此行为的解释:
之所以会发生这种情况,是因为当您调用sys.exit()
时会引发systemExit异常。由于sys.exit()
最终仅会引发异常,它只会退出以下过程:被调用,并且不会进一步传播到主要进程。
一旦所有子进程退出,主进程就坐在那里等待从子进程返回某些内容。所有子进程都已经退出,因此没有任何返回可导致永远的等待
答案 2 :(得分:0)
尝试使用os._exit(1)而不是sys.exit();