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Title: multiprocessing.Pool.__exit__() calls terminate() instead of close()
Type: behavior Stage: resolved
Components: Library (Lib) Versions: Python 3.7, Python 3.6, Python 3.3, Python 3.4, Python 3.5
Status: closed Resolution: wont fix
Dependencies: Superseder:
Assigned To: Nosy List: davin, josh.r, pitrou, s3rvac
Priority: normal Keywords:

Created on 2017-03-31 16:35 by s3rvac, last changed 2022-04-11 14:58 by admin. This issue is now closed.

Messages (3)
msg290923 - (view) Author: Petr Zemek (s3rvac) Date: 2017-03-31 16:35
multiprocessing.Pool.__exit__() calls terminate() instead of close(). Why? Wouldn't it be better (and more expected from a user's point of view) if it called close()?


- Calling close() would wait until all tasks are completed before shutting down the pool instead of terminating them abruptly when some of them may still be running.

- concurrent.futures.ProcessPoolExecutor.__exit__() calls shutdown(wait=True), which waits until all tasks are finished. In this regard, the behavior of Pool.__exit__() is inconsistent.

See also this comment by Dan O'Reilly (, who expressed an identical concern two years ago.
msg290951 - (view) Author: Josh Rosenberg (josh.r) * (Python triager) Date: 2017-04-01 01:05
I suspect it's far too late to change this, given compatibility constraints. If you want it to close instead of terminate, contextlib.closing is always an option.
msg290972 - (view) Author: Antoine Pitrou (pitrou) * (Python committer) Date: 2017-04-01 09:19
I agree it's far too late.  Multiple existing libraries may rely on the current behaviour.
Date User Action Args
2022-04-11 14:58:44adminsetgithub: 74140
2017-04-01 09:19:52pitrousetstatus: open -> closed

nosy: + pitrou
messages: + msg290972

resolution: wont fix
stage: resolved
2017-04-01 01:05:57josh.rsetnosy: + josh.r
messages: + msg290951
2017-03-31 16:45:11xiang.zhangsetnosy: + davin
2017-03-31 16:35:59s3rvaccreate