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weakref.WeakSet not instanceof collections.abc.Set #82942

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Septatrix mannequin opened this issue Nov 10, 2019 · 5 comments
Closed

weakref.WeakSet not instanceof collections.abc.Set #82942

Septatrix mannequin opened this issue Nov 10, 2019 · 5 comments
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@rhettinger
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3.9 only security fixes stdlib Python modules in the Lib dir type-feature A feature request or enhancement

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@Septatrix
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Mannequin

Septatrix mannequin commented Nov 10, 2019

BPO 38761
Nosy @gvanrossum, @rhettinger, @septatrix
PRs
  • WIP bpo-38761: Register WeakSet as a MutableSet #17104
    		•

    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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    GitHub fields:

    assignee = 'https://github.com/rhettinger'
closed_at = <Date 2019-11-11.04:13:30.075>
created_at = <Date 2019-11-10.11:39:15.194>
labels = ['type-feature', 'library', '3.9']
title = 'weakref.WeakSet not instanceof collections.abc.Set'
updated_at = <Date 2019-11-11.04:13:30.073>
user = 'https://github.com/Septatrix'

    bugs.python.org fields:

    activity = <Date 2019-11-11.04:13:30.073>
actor = 'rhettinger'
assignee = 'rhettinger'
closed = True
closed_date = <Date 2019-11-11.04:13:30.075>
closer = 'rhettinger'
components = ['Library (Lib)']
creation = <Date 2019-11-10.11:39:15.194>
creator = 'Nils Kattenbeck'
dependencies = []
files = []
hgrepos = []
issue_num = 38761
keywords = ['patch']
message_count = 5.0
messages = ['356326', '356337', '356343', '356349', '356350']
nosy_count = 3.0
nosy_names = ['gvanrossum', 'rhettinger', 'Nils Kattenbeck']
pr_nums = ['17104']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue38761'
versions = ['Python 3.9']
    @Septatrix
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    Septatrix mannequin commented Nov 10, 2019

    Instances of weakref.WeakSet are not instances of Set and therefore not of MutableSet but they are instances of Collection.
    They however implement all required methods for a MutableSet and Weak(Key|Value)Dictionary are correctly identified.
    Is this just an oversight or am I missing something?

    from weakref import WeakKeyDictionary, WeakValueDictionary, WeakSet
from collections.abc import MutableMapping, Collection, Set, MutableSet

wkdict = WeakKeyDictionary()
wvdict = WeakValueDictionary()
ws = WeakSet()

    assert isinstance(wkdict, MutableMapping)
    assert isinstance(wvdict, MutableMapping)
    assert isinstance(ws, Collection)
    assert not isinstance(ws, Set)
    assert not isinstance(ws, MutableSet)

    @Septatrix Septatrix mannequin added 3.7 (EOL) end of life stdlib Python modules in the Lib dir labels Nov 10, 2019
    @rhettinger
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    We could register the WeakSet in _collections_abc, right after MutableSet is defined. That module only registered builtins so that it can avoid imports; however, since we know that WeakSet is already loaded, it is reasonable to add an import for registration purposes.

    This was likely omitted because WeakSet is used in the implementation of the ABC.

    Marking this as a proposed enhancement rather than as a bug because the collections ABCs are under no obligation to register anything more than the builtins.

    @rhettinger rhettinger added 3.9 only security fixes and removed 3.7 (EOL) end of life labels Nov 10, 2019
    @rhettinger rhettinger self-assigned this Nov 10, 2019
    @rhettinger rhettinger added the type-feature A feature request or enhancement label Nov 10, 2019
    @gvanrossum
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    As I wrote between the lines in the PR, this would be a bug in the weakref module, not a bug in collections.abc.

    @rhettinger
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    New changeset 84ac437 by Raymond Hettinger in branch 'master':
    bpo-38761: Register WeakSet as a MutableSet (GH-17104)
    84ac437

    @rhettinger
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    Nils, thanks for the report.

    Guido, thanks for the clarification.

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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    @rhettinger rhettinger

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