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| author | Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> | 2020-06-10 20:33:59 (GMT) |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2020-06-10 20:33:59 (GMT) |
| commit | 18e07ba931c68eb5ab5262d4e57fe58c302686de (patch) | |
| tree | 8024070b583069950f3b6311ac248d250fddee30 | |
| parent | af6932575391bca10f4f2145b56e3edbe9765343 (diff) | |
| download | cpython-18e07ba931c68eb5ab5262d4e57fe58c302686de.zip cpython-18e07ba931c68eb5ab5262d4e57fe58c302686de.tar.gz cpython-18e07ba931c68eb5ab5262d4e57fe58c302686de.tar.bz2 | |
bpo-40895: Update weakref documentation to remove old warnings (GH-20687)
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>
| -rw-r--r-- | Doc/library/weakref.rst | 16 |
1 files changed, 0 insertions, 16 deletions
diff --git a/Doc/library/weakref.rst b/Doc/library/weakref.rst index 12eb985..d3c3a07 100644 --- a/Doc/library/weakref.rst +++ b/Doc/library/weakref.rst @@ -163,14 +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). - .. versionchanged:: 3.9 Added support for ``|`` and ``|=`` operators, specified in :pep:`584`. @@ -192,14 +184,6 @@ 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). - .. versionchanged:: 3.9 Added support for ``|`` and ``|=`` operators, as specified in :pep:`584`. |