Issue 28625: multiprocessing.Pool.imap swallows exceptions thrown by generators (original) (raw)

Issue28625

Created on 2016-11-06 16:16 by elias, last changed 2022-04-11 14:58 by admin. This issue is now closed.

Messages (4)
msg280146 - (view)	Author: Elias Zamaria (elias) *	Date: 2016-11-06 16:16
I have the following code: from multiprocessing import Pool def double(x): return 2 * x def get_numbers(): raise Exception("oops") yield 1 yield 2 print(list(Pool(processes=2).imap(double, get_numbers()))) I would expect it to raise an exception, but instead it just prints "[]", seeming to indicate that imap ran fine and produced no values. This seems similar to the behavior described in bugs 23051 and 26333, but this happens if the iterator directly raises an exception before yielding anything. If I move the raise statement below one or both of the yields, I get an exception from imap as expected. I am experiencing this with Python 3.5.2 on OS X 10.11.6. I haven't tried it with any other versions.
msg280913 - (view)	Author: Elias Zamaria (elias) *	Date: 2016-11-16 05:29
I tried my code in Python 3.6.0b3 and got the same result.
msg280957 - (view)	Author: Davin Potts (davin) *	Date: 2016-11-16 14:48
In , an important clue has been identified (a variation on the generator triggers a different, inconsistent behavior). I will merge this issue into that one to keep us all on the same page.
msg281744 - (view)	Author: Davin Potts (davin) *	Date: 2016-11-25 22:07
Closing this issue -- all further discussion moves to