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puneetdixit200 · 2026-05-26T11:47:49Z

Linked issue

Type of change

Bug fix (non-breaking change that fixes an issue)
Performance improvement (includes benchmark results below)
Documentation update
New feature or public API (requires prior proposal or issue approval)
Refactor / internal cleanup (no user-visible change)
Build, CI, or tooling change

Motivation

PythonObject.__contains__ currently implements membership in Mojo by checking __contains__ and otherwise iterating. The linked issue and maintainer guidance call for delegating membership to CPython through PySequence_Contains, which uses CPython sequence slots and fallback behavior directly.

What changed

Added a PySequence_Contains CPython binding, loader field, and wrapper.
Replaced PythonObject.__contains__ with a single PySequence_Contains call and Python error propagation on -1.
Added coverage for the raw binding, list/dict membership, a Python __contains__ implementation, iterator fallback, and non-iterable error propagation.

Testing

git diff --check HEAD~1..HEAD
./bazelw test //mojo/stdlib/test/python:test_python_object.mojo.test //mojo/stdlib/test/python:test_python_cpython.mojo.test could not run on this machine because Bazel exits before target analysis: error: a fully Xcode install must be selected globally, run sudo xcode-select -s /path/to/Xcode.app. This machine only has /Library/Developer/CommandLineTools selected and no /Applications/Xcode*.app.
./bazelw run format is blocked by the same Xcode preflight error.

Checklist

The linked issue above has been reviewed by a maintainer and is agreed-upon, or this is a trivial fix that does not need prior approval
PR is small and focused -- I have split larger changes into a sequence of smaller PRs where possible
I ran ./bazelw run format to format my changes
I added or updated tests to cover my changes
If AI tools assisted with this contribution, I have included an Assisted-by: trailer in my commit message or this PR description

Assisted-by: AI

BEGIN_PUBLIC [Stdlib] Use PySequence_Contains for Python membership Bind CPython PySequence_Contains and use it for PythonObject membership checks so list, dict, custom __contains__, and iterator fallback behavior stays delegated to CPython. Add Python interop coverage for the raw binding, __contains__, iterator fallback, and non-iterable error propagation. END_PUBLIC Assisted-by: AI Signed-off-by: Puneet Dixit <[email protected]>

Copilot

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR updates Mojo’s Python interop membership testing (in) to use CPython’s PySequence_Contains, and expands test coverage to validate correct behavior across __contains__ and __iter__ paths.

Changes:

Implement PythonObject.__contains__ via PySequence_Contains with proper error propagation.
Add a CPython binding/wrapper for PySequence_Contains.
Extend tests for membership semantics and adjust an overly-specific error substring assertion.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
mojo/stdlib/test/python/test_python_object.mojo	Adds new membership tests for `__contains__` and `__iter__`; loosens brittle error message match.
mojo/stdlib/test/python/test_python_cpython.mojo	Adds assertions covering `PySequence_Contains` results before/after list mutation.
mojo/stdlib/std/python/python_object.mojo	Replaces manual membership emulation with `PySequence_Contains` and raises on `-1`.
mojo/stdlib/std/python/_cpython.mojo	Introduces dynamic binding + CPython wrapper method for `PySequence_Contains`.

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Add coverage that a Python __contains__ exception propagates through Mojo membership. Assisted-by: AI Signed-off-by: Puneet Dixit <[email protected]>

Tighten the non-iterable membership assertion, broaden the test name, and keep the embedded Python source runtime-only. Assisted-by: AI Signed-off-by: Puneet Dixit <[email protected]>

github-actions · 2026-05-28T16:30:18Z

Thank you for your submission, we really appreciate it. Like many open-source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution. You can sign the CLA by just posting a Pull Request Comment same as the below format.

I have read the CLA Document and I hereby sign the CLA

_{You can retrigger this bot by commenting recheck in this Pull Request.}_{Posted by the CLA Assistant Lite bot.}

puneetdixit200 · 2026-05-28T16:30:53Z

Pushed cab7db0e9e84 with the review follow-up.

Changes:

tightened the non-iterable assertion to argument of type 'int' is not iterable\n- renamed test_contains_dunder to test_contains now that it covers dunder, iterator fallback, and propagation cases\n- changed CONTAINS_SOURCE from comptime to runtime var\n\nLocal verification: git diff --check. I still cannot run the stdlib test locally in this environment because the Mojo/Bazel/Pixi toolchain is not available here, so CI should validate the Mojo test run.

Apply the formatter's single-line style for the PySequence_Contains loader. Assisted-by: AI Signed-off-by: Puneet Dixit <[email protected]>

puneetdixit200 · 2026-05-28T16:44:10Z

Follow-up after CI lint: pushed 2f3e5e1dddf0 to apply the formatter diff for PySequence_Contains.load(self.lib.borrow()).

Current status: review threads are resolved, PR remains approved, lint/title/target/label checks pass. Build and Test on large-oss-linux is still pending, and CLAAssistant is failing on the external CLA signature gate.

Match the stable prefix of the non-container membership error so the test covers both current Python 3.14 wording and older Python wording. Assisted-by: AI Signed-off-by: Puneet Dixit <[email protected]>

puneetdixit200 · 2026-05-28T17:29:51Z

Pushed 2944d30234 to fix the branch-owned stdlib failure from the large build: Python 3.14 reports the int membership error as argument of type 'int' is not a container or iterable, so the test now matches the stable prefix shared with older Python wording.

Verification:

git diff --check

I could not run the Mojo/Bazel test locally because this environment has no mojo, pixi, bazel, or bazelisk executable. The other failed row in the previous large build was the unrelated max/tests/integration/cli:test_pipelines_cli_help_3.11 performance threshold at 1050.4 ms vs 1000 ms.

JoeLoser · 2026-05-28T22:01:14Z

Thank you for your submission, we really appreciate it. Like many open-source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution. You can sign the CLA by just posting a Pull Request Comment same as the below format.

I have read the CLA Document and I hereby sign the CLA

You can retrigger this bot by commenting recheck in this Pull Request. Posted by the CLA Assistant Lite bot.

Hi @puneetdixit200 - you'll need to sign our CLA before I can accept this contribution, please see the above.

puneetdixit200 requested a review from a team as a code owner May 26, 2026 11:47

Copilot AI review requested due to automatic review settings May 26, 2026 11:47

Copilot AI reviewed May 26, 2026

View reviewed changes

Comment thread mojo/stdlib/std/python/python_object.mojo

test(stdlib): cover membership error propagation

bece932

Add coverage that a Python __contains__ exception propagates through Mojo membership. Assisted-by: AI Signed-off-by: Puneet Dixit <[email protected]>

JoeLoser self-assigned this May 28, 2026

JoeLoser approved these changes May 28, 2026

View reviewed changes

Comment thread mojo/stdlib/test/python/test_python_object.mojo Outdated

Comment thread mojo/stdlib/test/python/test_python_object.mojo Outdated

Comment thread mojo/stdlib/test/python/test_python_object.mojo Outdated

JoeLoser added waiting for response Needs action/response from contributor before a PR can proceed Team: Mojo Libraries Relevant to the Mojo libraries team, which will review and decide on the issue or PR. labels May 28, 2026

test(stdlib): address membership review feedback

cab7db0

Tighten the non-iterable membership assertion, broaden the test name, and keep the embedded Python source runtime-only. Assisted-by: AI Signed-off-by: Puneet Dixit <[email protected]>

github-actions Bot added mojo-stdlib Tag for issues related to standard library waiting-on-review labels May 28, 2026

style(stdlib): format PySequence contains loader

2f3e5e1

Apply the formatter's single-line style for the PySequence_Contains loader. Assisted-by: AI Signed-off-by: Puneet Dixit <[email protected]>

test(stdlib): tolerate Python membership wording

2944d30

Match the stable prefix of the non-container membership error so the test covers both current Python 3.14 wording and older Python wording. Assisted-by: AI Signed-off-by: Puneet Dixit <[email protected]>

JoeLoser removed the Team: Mojo Libraries Relevant to the Mojo libraries team, which will review and decide on the issue or PR. label May 28, 2026

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[Stdlib] Use PySequence_Contains for Python membership#6609

[Stdlib] Use PySequence_Contains for Python membership#6609
puneetdixit200 wants to merge 5 commits into
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puneetdixit200:fix-3806-pysequence-contains

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puneetdixit200 commented May 26, 2026

Linked issue

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github-actions Bot commented May 28, 2026

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