Yes. Python 3.9 reached end of life on 31 October 2025, according to the Python developer guide. The core team no longer releases security fixes for it. If you still run 3.9, plan a move to a supported version such as 3.12, 3.13 or 3.14.
What the support calendar says
Python releases a new feature version every year and supports each for five years. The developer guide lists these end of life dates:
| Version | End of life | Note |
|---|---|---|
| 3.9 | 31 Oct 2025 | Ended |
| 3.10 | 1 Oct 2026 | Ended |
| 3.11 | Oct 2027 | Scheduled |
| 3.12 | Oct 2028 | Scheduled |
| 3.13 | Oct 2029 | Scheduled |
| 3.14 | Oct 2030 | Scheduled |
The guide says dates in italics are scheduled and can be adjusted, so recheck before you commit to a long plan. We have a separate post on the 3.10 end of life.
Why it matters even for private code
The interpreter is not the only part that ages. Libraries drop old Python versions, usually a year or two after the interpreter does. When you pin to 3.9, you eventually stop getting new releases of your dependencies, including their security fixes. So an old interpreter quietly freezes your whole dependency tree.
How to choose the target
Pick the newest version your key libraries support, not the oldest that is still supported. A newer target gives you more years before the next forced move. Check the classifiers on your main packages, then run your tests under two candidate versions.
Upgrade steps
- Search for the version everywhere: Dockerfiles, CI,
pyproject.toml,.python-version, tox files and base images. - Turn on deprecation warnings in tests with
python -W error::DeprecationWarning -m pytestand fix what surfaces. - Upgrade pip tooling and regenerate your lock file on the new version.
- Run tests in CI on old and new versions side by side for a few days.
- Rebuild wheels for any compiled dependencies.
- Switch deployment, then remove the old version from CI.
Try it yourself
Open the demo and note how each dependency shows its version, which tells you what an old interpreter is holding back.
Click through it at your own pace, or open it full screen.
Quick check
Will Python 3.9 code run on Python 3.12?
Mostly yes, but removed modules and changed behaviour can break specific code. The test run with deprecation warnings enabled will show you where.
Do virtual environments protect me from an old interpreter?
No. A virtual environment isolates packages, not the interpreter. It still runs the end of life Python underneath.
Where Safeguard fits
Safeguard's dependency scanning reads your lock files and manifests, so you can see which projects pin which Python-era dependencies before you start. A free scan is a quick way to get that first list.
Sources
Last reviewed: 19 October 2026.
