Message 370860 - Python tracker

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Author	dfortunov
Recipients	dfortunov, docs@python
Date	2020-06-06.23:23:07
SpamBayes Score	-1.0
Marked as misclassified	Yes
Message-id	<1591485787.87.0.566129309531.issue40895@roundup.psfhosted.org>
In-reply-to

Content
The doccumentation at https://docs.python.org/3.10/library/weakref.html cautions that the WeakKeyDictionary and WeakValueDictionary are susceptible to the problem of dictionary mutation during iteration. These notes present the user with a problem that has no easy solution. I dug into the implementation and found that fortunately, Antoine Pitrou already addressed this challenge (10 years ago!) by introducing an _IterationGuard context manager to the implementation, which delays mutation while an iteration is in progress. I asked for confirmation and Antoine agreed that these notes could be removed: https://github.com/python/cpython/commit/c1baa601e2b558deb690edfdf334fceee3b03327#commitcomment-39514438

The doccumentation at https://docs.python.org/3.10/library/weakref.html cautions that the WeakKeyDictionary and WeakValueDictionary are susceptible to the problem of dictionary mutation during iteration.

These notes present the user with a problem that has no easy solution.

I dug into the implementation and found that fortunately, Antoine Pitrou already addressed this challenge (10 years ago!) by introducing an _IterationGuard context manager to the implementation, which delays mutation while an iteration is in progress.

I asked for confirmation and Antoine agreed that these notes could be removed:
https://github.com/python/cpython/commit/c1baa601e2b558deb690edfdf334fceee3b03327#commitcomment-39514438

History
Date	User	Action	Args
2020-06-06 23:23:07	dfortunov	set	recipients: + dfortunov, docs@python
2020-06-06 23:23:07	dfortunov	set	messageid: <1591485787.87.0.566129309531.issue40895@roundup.psfhosted.org>
2020-06-06 23:23:07	dfortunov	link	issue40895 messages
2020-06-06 23:23:07	dfortunov	create