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Implement PEP 661 Sentinel Values #148829
Description
Feature or enhancement
Proposal:
PEP-661 has not been accepted (python/steering-council#258), but I hope to still get it in for 3.15, and in view of the short time window available I'd like to already submit a PR so those interested can review the implementation already while the SC deliberates.
Has this already been discussed elsewhere?
No response given
Links to previous discussion of this feature:
No response
Linked PRs
- gh-148829: Implement PEP 661 #148831
- gh-148829: bump number of static types #149121
- gh-148829: Move sentinelobject.h to Include/cpython/ #149186
- gh-148829: Make sentinels' repr and module customizable #149654
- gh-148829: Add PySentinel_CheckExact() #149725
- [3.15] gh-148829: Add PySentinel_CheckExact() (GH-149725) #149766
- [3.15] gh-148829: Make sentinels' repr and module customizable (GH-149654) #150092
Reacted by M. Kocher and Harmon
Activity
hugovk commentedon Apr 21, 2026
And I'll be happy if any buildbot failures can be found before any last-minute merge on release day :)
gh-148829: Implement PEP 661 (#148831)
gh-148829: bump number of static types (#149121)
scoder commentedon Apr 29, 2026
Was it considered to add a macro alias
PySentinel_CheckExact(o)forPySentinel_Check(o)?Or is there an inherent reason why the sentinel type will never, ever allow inheritance?
hugovk commentedon Apr 29, 2026
There's discussion about subclassing at https://discuss.python.org/t/pep-661-sentinel-values/9126/341: not now, maybe later.
gh-148829: Move sentinelobject.h to Include/cpython/ (#149186)
gh-148829: Add PySentinel_CheckExact() (#149725)
[3.15] gh-148829: Add PySentinel_CheckExact() (GH-149725) (#149766)
gh-148829: Make sentinels' repr and module customizable (#149654)
[3.15] gh-148829: Make sentinels' repr and module customizable (GH-14…