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GeezerVison is showing github.com — gh-148639: Implement PEP 800 (typing.disjoint_base) by JelleZijlstra · Pull Request #148640 · python/cpython

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@JelleZijlstra

@JelleZijlstra JelleZijlstra commented Apr 16, 2026 •
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  • Issue: Implement PEP 800: typing.disjoint_base #148639

📚 Documentation preview 📚: https://cpython-previews--148640.org.readthedocs.build/

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@JelleZijlstra
pythongh-148639: Implement PEP 800 (typing.disjoint_base)
3f7202c
@JelleZijlstra
JelleZijlstra requested review from AA-Turner, AlexWaygood and willingc as code owners April 16, 2026 03:09
@bedevere-app bedevere-app Bot added the awaiting core review label Apr 16, 2026
@bedevere-app bedevere-app Bot mentioned this pull request Apr 16, 2026
Implement PEP 800: typing.disjoint_base #148639
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JelleZijlstra added 2 commits April 15, 2026 20:10
@JelleZijlstra
did not end up using that
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@JelleZijlstra
blurb
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Viicos
Viicos reviewed Apr 16, 2026
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Comment thread Doc/library/typing.rst Resolved

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Comment thread Lib/typing.py Resolved

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encukou
encukou reviewed Apr 16, 2026
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Comment thread Doc/library/typing.rst Resolved

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JelleZijlstra and others added 3 commits April 16, 2026 05:51
@JelleZijlstra @Viicos
Apply suggestion from @Viicos
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Co-authored-by: Victorien <[email protected]>
@JelleZijlstra @encukou
Update Doc/library/typing.rst
90b4418 
Co-authored-by: Petr Viktorin <[email protected]>
@JelleZijlstra
Merge branch 'python:main' into pep800
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carljm
carljm approved these changes Apr 17, 2026
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LGTM, thank you!

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Comment thread Lib/typing.py Outdated
"""This decorator marks a class as a disjoint base.

Child classes of a disjoint base cannot inherit from other disjoint bases that are
not parent classes of the disjoint base.

@carljm carljm Apr 17, 2026

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I think we need to say "parent or child" here, not just "parent", similar to the documentation wording.

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Comment thread Doc/library/typing.rst Outdated
Type checkers do not allow child classes of a disjoint base ``C`` to
inherit from other disjoint bases that are not parent or child classes of ``C``.

For example:

@carljm carljm Apr 17, 2026

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I think we either need a double colon here or a .. testcode:: directive, for this example to render properly?

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@JelleZijlstra JelleZijlstra Apr 18, 2026

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Good call, double colon works

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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting core review labels Apr 17, 2026
@JelleZijlstra
fixes
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@JelleZijlstra
JelleZijlstra merged commit 92164dc into python:main Apr 18, 2026
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@bedevere-app bedevere-app Bot removed the awaiting merge label Apr 18, 2026
@JelleZijlstra
JelleZijlstra deleted the pep800 branch April 18, 2026 02:20
ljfp pushed a commit to ljfp/cpython that referenced this pull request Apr 25, 2026
@JelleZijlstra @Viicos
@encukou @ljfp
pythongh-148639: Implement PEP 800 (typing.disjoint_base) (python#148640
5ec4032 
)

Co-authored-by: Victorien <[email protected]>
Co-authored-by: Petr Viktorin <[email protected]>
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@encukou encukou encukou left review comments
@carljm carljm carljm approved these changes
@AlexWaygood AlexWaygood Awaiting requested review from AlexWaygood AlexWaygood is a code owner
@AA-Turner AA-Turner Awaiting requested review from AA-Turner AA-Turner is a code owner
@willingc willingc Awaiting requested review from willingc
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@Viicos Viicos Viicos left review comments
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@JelleZijlstra @carljm @encukou @Viicos
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