PYTHON-6077 Officially support Python 3.15 by blink1073 · Pull Request #3042 · mongodb/mongo-python-driver

blink1073 · 2026-09-05T00:00:31Z

PYTHON-6077

Changes in this PR

Added Python 3.15 (standard and free-threaded) to the Evergreen test matrix and wheel builds.
Standardized interpreter selection on UV_PYTHON, preferring the toolchain and fetching missing builds, such as the 3.15 pre-release, from python-build-standalone.
Fixed enterprise-auth keytab decoding for Python 3.15's stricter base64.
Added the Python 3.15 classifier and changelog entry.
Most of the lines of code in the diff are from the regenerated tasks spanning the new python verisons.

Test Plan

Ran an Evergreen patch; the python-build-standalone fallback resolves the 3.15 builds.

Checklist

Checklist for Author

Did you update the changelog (if necessary)?
Is there test coverage? Added Evergreen CI coverage for the new versions.
Is any followup work tracked in a JIRA ticket? If so, add link(s). Drop the python-build-standalone fallback once the toolchain provides 3.15.

Checklist for Reviewer

Does the title of the PR reference a JIRA Ticket?
Do you fully understand the implementation? (Would you be comfortable explaining how this code works to someone else?)
Is all relevant documentation (README or docstring) updated?

…7-officially-support-py315 # Conflicts: # .evergreen/generated_configs/tasks.yml

This reverts commit 78b8a2e.

codecov · 2026-09-05T01:47:57Z

Codecov Report

❌ Patch coverage is 55.55556% with 12 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
pymongo/network_layer.py	55.55%	12 Missing ⚠️

📢 Thoughts on this report? Let us know!

…version

blink1073 · 2026-09-08T13:12:51Z

            write_env("KRB5_CONFIG", krb_conf)
            LOGGER.info("Writing keytab")
-            keytab = base64.b64decode(config["KEYTAB_BASE64"])
+            keytab_b64 = config["KEYTAB_BASE64"]


This change was needed for Python 3.15 support

Copilot

🟡 Changes recommended

The fallback selects a 64-bit interpreter for Win32 coverage and performs avoidable rate-limited API requests.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Adds official Python 3.15 and free-threaded 3.15 support across packaging and CI.

Changes:

Adds Python 3.15 metadata, changelog, tests, and wheels.
Standardizes CI interpreter selection through UV_PYTHON.
Adds a python-build-standalone fallback and stricter keytab decoding.

File summaries

File	Description
`pyproject.toml`	Adds the Python 3.15 classifier.
`doc/changelog.rst`	Documents Python 3.15 support.
`.github/workflows/dist.yml`	Builds and verifies 3.15 wheels.
`.evergreen/scripts/setup-uv-python.sh`	Resolves toolchain interpreters.
`.evergreen/scripts/setup-dev-env.sh`	Installs or fetches missing interpreters.
`.evergreen/scripts/setup_tests.py`	Corrects keytab Base64 padding.
`.evergreen/scripts/generate_config.py`	Generates `UV_PYTHON`-based tasks.
`.evergreen/scripts/generate_config_utils.py`	Defines 3.15 versions and helpers.
`.evergreen/scripts/fetch-python.sh`	Fetches standalone Python builds.
`.evergreen/generated_configs/variants.yml`	Adds 3.15 compression variants.
`.evergreen/generated_configs/tasks.yml`	Adds and migrates generated tasks.
`.evergreen/generated_configs/functions.yml`	Propagates `UV_PYTHON`.

Review details

Suppressed comments (1)

.evergreen/scripts/fetch-python.sh:35

This unauthenticated GitHub API request runs before the existing-install check at line 53, so every repeated setup still consumes a request even after the large interpreter has been cached. Python 3.15 tasks source this setup more than once, making shared CI egress susceptible to GitHub's unauthenticated rate limit and causing otherwise cached jobs to fail. Resolve the cache path and return it before querying the release API, or cache the release metadata separately.

release="$(curl -fsSL --retry 3 https://api.github.com/repos/astral-sh/python-build-standalone/releases/latest)"

Files reviewed: 11/12 changed files
Comments generated: 1
Review effort level: Balanced

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Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Copilot

🟡 Changes recommended

The new python-build-standalone fallback currently sets UV_PYTHON to a directory (not an interpreter path), which is inconsistent with how UV_PYTHON is handled elsewhere and can break uv run interpreter selection.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review details

Suppressed comments (1)

Previously missed (1) — in code that hasn't changed since the last review.

doc/changelog.rst:4

The changelog header uses an invalid date placeholder ("2026/XX/XX"), which can be confusing and may break tooling that expects a real date. Consider using an explicit "Unreleased" marker until the release date is known.

Files reviewed: 11/12 changed files
Comments generated: 1
Review effort level: Lite

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

…7-officially-support-py315 # Conflicts: # doc/changelog.rst

Run async KMS SSL send/recv via loop.run_in_executor with the socket in blocking mode, mirroring the synchronous socket path. This replaces the hand-rolled add_reader/add_writer non-blocking machinery that surfaces a peer reset as a raw ConnectionResetError/BrokenPipeError (before any bytes are sent) under asyncio on Python 3.15, breaking async-only KMS-TLS tests on macOS and rhel8. Also remove the temporary [KMS-DEBUG] diagnostics.

Remove the leftover [KMS-DEBUG] block in pool_shared._async_configured_socket. In network_layer, use asyncio.shield around the executor future in _async_blocking_socket_call so wait_for cannot cancel it. On timeout, join the worker (bounded by the socket's own timeout) before propagating, so the caller never closes the SSL socket out from under the worker thread - closing an in-flight SSL socket is racy and not thread-safe. Handle CancelledError from re-awaiting the shielded future, and restore the non-blocking timeout dance for the plain (non-TLS) socket branch.

On Python 3.15 (OpenSSL 3.x), a peer that resets the connection during async KMS send/recv surfaces as BrokenPipeError/ConnectionResetError, where older Pythons (OpenSSL 1.1.1) surfaced a clean EOF. Map these to OSError("connection closed") in _async_blocking_socket_call so KMS requests treat a reset as a retryable connection failure, matching the behavior on earlier Pythons and the sync path. Fixes the async TestKmsTLSOptions KMIP cases on Python 3.15.

blink1073 added 6 commits September 4, 2026 11:11

PYTHON-6077 Officially support Python 3.15

11f1822

PYTHON-6077 Always use UV_PYTHON and prefer toolchain pythons

82afc1a

Merge remote-tracking branch 'upstream/main' into worktree-PYTHON-607…

4098a2e

…7-officially-support-py315 # Conflicts: # .evergreen/generated_configs/tasks.yml

PYTHON-6077 Drop the python-build-standalone fallback for 3.15

78b8a2e

Revert "PYTHON-6077 Drop the python-build-standalone fallback for 3.15"

620507f

This reverts commit 78b8a2e.

PYTHON-6077 Handle remaining 3.15 CI failures

f6be3d0

blink1073 added 2 commits September 8, 2026 07:54

PYTHON-6077 Generalize python-build-standalone fetch for any missing …

4841077

…version

PYTHON-6077 Clarify python download conditions in setup-dev-env

2a2c0c6

blink1073 commented Sep 8, 2026

View reviewed changes

blink1073 requested a balanced review from Copilot September 8, 2026 13:14

Copilot started reviewing on behalf of blink1073 September 8, 2026 13:14 View session

Copilot AI reviewed Sep 8, 2026

View reviewed changes

Comment thread .evergreen/scripts/fetch-python.sh

Handle x86_64 architecture for Windows and others

a70b3a5

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

blink1073 requested a lite review from Copilot September 8, 2026 13:27

Copilot started reviewing on behalf of blink1073 September 8, 2026 13:28 View session

Copilot AI reviewed Sep 8, 2026

View reviewed changes

Comment thread .evergreen/scripts/setup-dev-env.sh Outdated

blink1073 and others added 13 commits September 8, 2026 08:36

Refactor Python interpreter setup in setup-dev-env.sh

5a34041

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

PYTHON-6077 Fix missing fi in setup-dev-env.sh

f3acdf1

PYTHON-6077 Accept unpadded/whitespace-padded keytab on 3.15

133c3bb

PYTHON-6077 Strip internal whitespace from keytab base64

1f56904

PYTHON-6077 Decode keytab with lenient padding on 3.15

473ed18

Merge remote-tracking branch 'upstream/main' into worktree-PYTHON-607…

6501c2f

…7-officially-support-py315 # Conflicts: # doc/changelog.rst

PYTHON-6077 Make test_list_collections robust to empty test db

778de06

PYTHON-6077 Clone drivers-tools module regardless of env.sh

27bcd1e

PYTHON-6077 Use PATH-based Python resolution with bare UV_PYTHON

269e79b

PYTHON-6077 Scope UV_PYTHON_PREFERENCE=system to non-Windows

95e0e90

PYTHON-6077 Use path-based UV_PYTHON on Windows

ea36a45

PYTHON-6077 Skip fetch fallback on re-entry by marking Python resolved

461b5b1

PYTHON-6077 Add KMS-DEBUG ssl diagnostics (temporary)

81ca2a4

blink1073 added 6 commits September 9, 2026 05:25

PYTHON-6077 Treat path UV_PYTHON as already resolved

3c6ec12

PYTHON-6077 Exclude 3.15t from encryption and pyopenssl variants

a95b78e

PYTHON-6077 Add rich KMS-DEBUG socket diagnostics (temporary)

0dc5704

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PYTHON-6077 Officially support Python 3.15 - #3042

PYTHON-6077 Officially support Python 3.15#3042
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