bpo-40895: Update weakref documentation to remove old warnings by asqui · Pull Request #20687 · python/cpython (original) (raw)

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 @pitrou agreed that these notes could be removed:
c1baa60#commitcomment-39514438

https://bugs.python.org/issue40895

Automerge-Triggered-By: @pitrou