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bpo-46342: make @typing.final introspectable#30530

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gvanrossum merged 4 commits intopython:mainfrom
JelleZijlstra:issue46342
Jan 12, 2022
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bpo-46342: make @typing.final introspectable#30530
gvanrossum merged 4 commits intopython:mainfrom
JelleZijlstra:issue46342

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@JelleZijlstra JelleZijlstra commented Jan 11, 2022 •
edited by bedevere-bot
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JelleZijlstra
JelleZijlstra commented Jan 11, 2022
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Lib/typing.py
"""
try:
f.__final__ = True
except (AttributeError, TypeError):
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@JelleZijlstra JelleZijlstra Jan 11, 2022

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I'd be open to just doing just except Exception here, in case some type throws a different exception if you try to set an attribute. For precedent, note that @no_type_check catches only TypeError.

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Fidget-Spinner commented Jan 11, 2022

LGTM.
Side question: I'm curious as to which runtime type checkers use this information/What inspired you to make this change?

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JelleZijlstra commented Jan 11, 2022

quora/pyanalyze#161. My type checker, pyanalyze, imports modules it typechecks and uses the runtime objects for checking. With this change, I can make it show an error if you inherit from something @final.

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Fidget-Spinner reviewed Jan 11, 2022
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Some minor nits

Fidget-Spinner
Fidget-Spinner reviewed Jan 11, 2022
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gvanrossum
gvanrossum reviewed Jan 11, 2022
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Sounds like a good idea. I trust the current participants to come up with the right thing. Let me know when you all agree and you want me to merge it.

Fidget-Spinner
Fidget-Spinner approved these changes Jan 12, 2022
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LGTM. Thanks Jelle.

@gvanrossum gvanrossum merged commit 0bbf30e into python:main Jan 12, 2022
@JelleZijlstra JelleZijlstra deleted the issue46342 branch January 12, 2022 19:38
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@gvanrossum gvanrossum gvanrossum approved these changes

@Fidget-Spinner Fidget-Spinner Fidget-Spinner approved these changes

@AlexWaygood AlexWaygood AlexWaygood approved these changes

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6 participants

@JelleZijlstra @Fidget-Spinner @gvanrossum @AlexWaygood @the-knights-who-say-ni @bedevere-bot