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| author | Antoine Pitrou <antoine@python.org> | 2020-06-10 20:38:42 (GMT) |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2020-06-10 20:38:42 (GMT) |
| commit | 972aba86ede0bf254e16a760639a1ff8df298578 (patch) | |
| tree | ace62bca837a44714ba27b2e823351480d49b566 /Doc/library | |
| parent | c7a6c7b5279f766e65b7cc9dc5bebb73acee6672 (diff) | |
| download | cpython-972aba86ede0bf254e16a760639a1ff8df298578.zip cpython-972aba86ede0bf254e16a760639a1ff8df298578.tar.gz cpython-972aba86ede0bf254e16a760639a1ff8df298578.tar.bz2 | |
[3.8] bpo-40895: Update weakref documentation to remove old warnings (GH-20687) (GH-20792)
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:
https://github.com/python/cpython/commit/c1baa601e2b558deb690edfdf334fceee3b03327GH-commitcomment-39514438.
(cherry picked from commit 1642c0ef750f96664a98cadb09301d492098d2fb)
Co-authored-by: Daniel Fortunov <asqui@users.noreply.github.com>
Automerge-Triggered-By: @pitrou
Diffstat (limited to 'Doc/library')
| -rw-r--r-- | Doc/library/weakref.rst | 14 |
1 files changed, 0 insertions, 14 deletions
diff --git a/Doc/library/weakref.rst b/Doc/library/weakref.rst index 2dbe5e3..0d9f21d 100644 --- a/Doc/library/weakref.rst +++ b/Doc/library/weakref.rst @@ -163,13 +163,6 @@ Extension types can easily be made to support weak references; see application without adding attributes to those objects. This can be especially useful with objects that override attribute accesses. - .. note:: - - Caution: Because a :class:`WeakKeyDictionary` is built on top of a Python - dictionary, it must not change size when iterating over it. This can be - difficult to ensure for a :class:`WeakKeyDictionary` because actions - performed by the program during iteration may cause items in the - dictionary to vanish "by magic" (as a side effect of garbage collection). :class:`WeakKeyDictionary` objects have an additional method that exposes the internal references directly. The references are not guaranteed to @@ -189,13 +182,6 @@ than needed. Mapping class that references values weakly. Entries in the dictionary will be discarded when no strong reference to the value exists any more. - .. note:: - - Caution: Because a :class:`WeakValueDictionary` is built on top of a Python - dictionary, it must not change size when iterating over it. This can be - difficult to ensure for a :class:`WeakValueDictionary` because actions performed - by the program during iteration may cause items in the dictionary to vanish "by - magic" (as a side effect of garbage collection). :class:`WeakValueDictionary` objects have an additional method that has the same issues as the :meth:`keyrefs` method of :class:`WeakKeyDictionary` |