[New-bugs-announce] [issue44140] WeakKeyDictionary should support lookup by id instead of hash

conchylicultor report at bugs.python.org
Sat May 15 04:42:51 EDT 2021

New submission from conchylicultor <etiennefg.pot at gmail.com>:

WeakKeyDictionary are great to "associate additional data with an object owned by other parts of an application", as quoted from the doc: https://docs.python.org/3/library/weakref.html#weakref.WeakKeyDictionary

However, this currently only works for hashable types. Non-hashables are not supported:

class A:

a = A()

d = weakref.WeakKeyDictionary()
d[a] = 3  # TypeError: unhashable type: 'A'

With regular dict, this could be easilly solved by using `d[id(a)] = 3`, but WeakKeyDictionary don't accept `int` of course. I cannot wrap the object either as the weakref would not be attached to the original object, but the wrapper.

It would be great to be able to force WeakKeyDictionary to perform lookup on `id` internally. Like `d = WeakKeyDictionary(use_id_lookup=True)`

components: Library (Lib)
messages: 393707
nosy: conchylicultor
priority: normal
severity: normal
status: open
title: WeakKeyDictionary should support lookup by id instead of hash
type: enhancement
versions: Python 3.10, Python 3.11, Python 3.6, Python 3.7, Python 3.8, Python 3.9

Python tracker <report at bugs.python.org>

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