register contextvars.Context to collections.abc.Mapping

[tungol]

Feature or enhancement

Proposal:

contextvars.Context is documented as implementing the collections.abc.Mapping interface. I believe we should register it to the abc, so an isinstance check can work.

This is similar to #126417 .

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

A small amount of prior discussion occurred in an issue for typeshed: python/typeshed#12873

Linked PRs

• gh-126451: Register contextvars.Context to collections.abc.Mapping #126452
• [3.13] gh-126451: Register contextvars.Context to collections.abc.Mapping (GH-126452) #126518
• [3.12] gh-126451: Register contextvars.Context to collections.abc.Mapping (GH-126452) #126519
• [3.13] gh-126451: Revert backports of ABC registrations for contextvars.Context and multiprocessing proxies #126734
• [3.12] gh-126451: Revert backports of ABC registrations for contextvars.Context and multiprocessing proxies #126735

[JelleZijlstra]

Could you list out all the methods on Mapping to confirm it really conforms with the interface? I'd like to prevent another case similar to #125420.

[tungol]

Sure.

Mapping methods are: __getitem__, __iter__, __len__, __contains__, keys, items, values, get, __eq__, and __ne__. All are present on Context:

>>> from contextvars import Context
>>> Context.__getitem__
<slot wrapper '__getitem__' of '_contextvars.Context' objects>
>>> Context.__iter__
<slot wrapper '__iter__' of '_contextvars.Context' objects>
>>> Context.__len__
<slot wrapper '__len__' of '_contextvars.Context' objects>
>>> Context.__contains__
<slot wrapper '__contains__' of '_contextvars.Context' objects>
>>> Context.keys
<method 'keys' of '_contextvars.Context' objects>
>>> Context.items
<method 'items' of '_contextvars.Context' objects>
>>> Context.values
<method 'values' of '_contextvars.Context' objects>
>>> Context.get
<method 'get' of '_contextvars.Context' objects>
>>> Context.__eq__
<slot wrapper '__eq__' of '_contextvars.Context' objects>
>>> Context.__ne__
<slot wrapper '__ne__' of '_contextvars.Context' objects>