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GH-143493: Conform to spec for generator expressions while supporting virtual iterators by markshannon · Pull Request #143569 · python/cpython · GitHub

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GH-143493: Conform to spec for generator expressions while supporting virtual iterators - #143569

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markshannon merged 3 commits into
python:mainfrom
markshannon:genexpr-conform-to-spec-fast
Jan 16, 2026
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GH-143493: Conform to spec for generator expressions while supporting virtual iterators#143569
markshannon merged 3 commits into
python:mainfrom
markshannon:genexpr-conform-to-spec-fast

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markshannon commented Jan 8, 2026 •
edited by bedevere-app Bot
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  • Moves the GET_ITER instruction into the generator function preamble. This means the the iterable is converted into an iterator during generator creation, as documented, but keeps it in the same code object allowing optimization.

Conform to spec for generator expressions while supporting virtual it…
4deca76 
…erators

* Moves the `GET_ITER` instruction into the generator function preamble.
  This means the the iterable is converted into an iterator during generator
  creation, as documented, but keeps it in the same code object allowing
  optimization.
bedevere-app Bot mentioned this pull request Jan 8, 2026
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serhiy-storchaka reviewed Jan 9, 2026
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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

Sorry, the code was changed so much since I worked with it, that I can no longer make qualified review. I can understand particular changes, but I cannot catch if something was missed. The original idea looks reasonably.

BTW, what happens when __iter__() raises StopIteration?

Is similar change needed for asynchronous generators?

markshannon commented Jan 9, 2026 •
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BTW, what happens when __iter__() raises StopIteration?

The exception is raised before the generator is created and the traceback shows the iterable as the location of the exception.

markshannon commented Jan 9, 2026

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Is similar change needed for asynchronous generators?

I don't think asynchronous generators were ever changed, so they still have the old behavior from 3.13 and earlier.

DinoV approved these changes Jan 15, 2026
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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

Other than the one nit looks good to me

Comment thread Python/codegen.c Outdated
int gen_index, int depth,
expr_ty elt, expr_ty val, int type,
int iter_on_stack)
IterStackState iter_on_stack)

DinoV Jan 14, 2026

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

nit: Is it worth renaming these to something like iter_state like it is in codegen_comprehension?

markshannon Jan 15, 2026 •
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It isn't it state, it is its location. Maybe I'll rename IterStackState instead.

python deleted a comment from J2085isa Jan 15, 2026
markshannon merged commit ae53da5 into python:main Jan 16, 2026
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bedevere-bot commented Jan 16, 2026

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⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot ARM64 macOS 3.x (tier-2) has failed when building commit ae53da5.

What do you need to do:

  1. Don't panic.
  2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
  3. Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/725/builds/12565) and take a look at the build logs.
  4. Check if the failure is related to this commit (ae53da5) or if it is a false positive.
  5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/725/builds/12565

Failed tests:

  • test_urllib2net

Failed subtests:

  • test_call_count_thread_safe - test.test_unittest.testmock.testthreadingmock.TestThreadingMock.test_call_count_thread_safe
  • test_preauth_data_to_tls_server - test.test_ssl.TestPreHandshakeClose.test_preauth_data_to_tls_server

Summary of the results of the build (if available):

==

Click to see traceback logs 
Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/test_ssl.py", line 5476, in test_preauth_data_to_tls_server
    self.assertIn("before TLS handshake with data", wrap_error.args[1])
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 'before TLS handshake with data' not found in '[SSL: RECORD_LAYER_FAILURE] record layer failure (_ssl.c:1096)'


Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/test_unittest/testmock/testthreadingmock.py", line 219, in test_call_count_thread_safe
    self.assertEqual(m.call_count, LOOPS * THREADS)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 998 != 1000

DinoV mentioned this pull request Jan 16, 2026
Merged
meta-codesync Bot pushed a commit to facebookincubator/cinderx that referenced this pull request Jan 21, 2026
Update for future upstream changes
61b4aeb 
Summary: python/cpython#143569 has fixed a bug introduced in the code gen where passing a non-iterable to a generator doesn't raise immediately. This matches the code gen.

Reviewed By: mpage

Differential Revision: D90706769

fbshipit-source-id: 229a355c62e4b07ca0f3853ba91ac31b81946a8b
meta-codesync Bot pushed a commit to facebookincubator/cinderx that referenced this pull request Jan 22, 2026
Fix the CinderX 3.15 build
92da407 
Summary:
Fixes up the CinderX build after the latest import. This brought in python/cpython#142911 which move somethings into ceval.h so that we can directly include it rather than borrowing those functions. We bring back `cinderx-only-headers` and now use them on 3.10 and 3.15+.

There's also a fix related to python/cpython#143569 where we need to update the interpreter loop.

Also python/cpython@bb25f72 seems to have refactored `_PyDict_LookupIndex` to use `_PyDict_LookupIndexAndValue`.

There's some more work after this to further reduce our usage of `ceval_macros.h` but this just gets things working again.

Reviewed By: itamaro

Differential Revision: D91146024

fbshipit-source-id: 6da3ef18fe5fe5f79e29a71cdbe98491bbb45a9d
thunder-coding pushed a commit to thunder-coding/cpython that referenced this pull request Feb 15, 2026
pythonGH-143493: Conform to spec for generator expressions while supp…
f2185b1 
…orting virtual iterators (pythonGH-143569)

* Moves the `GET_ITER` instruction into the generator function preamble.
  This means the the iterable is converted into an iterator during generator
  creation, as documented, but keeps it in the same code object allowing
  optimization.
iritkatriel mentioned this pull request Aug 25, 2026
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serhiy-storchaka serhiy-storchaka left review comments
DinoV DinoV approved these changes
iritkatriel Awaiting requested review from iritkatriel iritkatriel is a code owner
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