Picking a Python version for a project

When the work on this book started, Python 3.11 was selected as the language version that code would be written in. There were several reasons for that selection, but the primary one was that it had been available for long enough to be in a security maintenance cycle, and with no expectation of significant changes other than for security issues. That was early in 2024, and support for the version is, as the book is being finished, going to continue for another two years, ending in October of 2027. Hand in hand with that was the fact that the bulk of the work I was doing was writing and maintaining AWS Lambda Functions written in Python, and although the 3.12 version was available for those purposes, it was new enough that I didn’t have a lot of hands-on experience with it in that context.

The Python Software Foundation, the maintainers of the language, have historically been very good about publishing comprehensive documentation of the changes to the language as each new minor version is released. Their documentation for any given version can be found online at https://www.python.org/doc/versions/, and is updated as each new version is released, including the patch versions.

Python’s release schedule and support processes are well documented online (see https://devguide.python.org/versions/), with a cadence of approximately five years between the initial release of a minor version and its official end of life. In more recent versions, the first two years or so of a given version’s life include a bugfix support phase, and the remaining three years are limited to security support. Online providers will frequently follow the life cycle of any given Python version with respect to their support of that version, though they may allow continued use of a version that has officially reached its end of life. By way of example, Amazon Web Services’ (AWS’) Python version support, as of the end of 2025, included Python 3.9, with an official end of life in October of 2025, was a supported version, with its deprecation planned in December 2025, and limitations on the ability to create or update Lambda Functions using that version starting early in 2026.

So, taking all of these factors into consideration, the determination of what Python version to use for any given project is a decision that needs to be made based on a number of factors:

• As a general rule, the most recent version available may be preferable, simply because it will provide the most current capabilities that the language provides, and will have the longest lifespan.
• Restrictions or constraints by a provider may limit those options: Using AWS as an example again, they appear to start supporting a given version of Python about a month after it is released, but that may not always be the case. Other providers may have different limitations, or it may be that the OS where development work is being done imposes its own limitation (not uncommon for Linux systems that use Python for key applications or tools).
• Even if a just-released new version is supported, there is some risk assessment that should be undertaken: The bugfix phase of the version will last for two years, and there is some risk that bug fixes implemented during that period will be problematic. The same holds true for versions that are in the security phase of their lives, though generally those have fewer issues on a release-by-release basis, likely because most of the bugs have already been dealt with by then.
• Checking the Changelog for a given version (https://docs.python.org/release/3.11.13/whatsnew/changelog.html, for example, for 3.11), or the release notes (https://docs.python.org/3/whatsnew/3.11.html for 3.11 again) may also be useful if there are specific features that are needed or desired in the project, that may not be available or implemented as expected.

As of the end of 2025, assuming that the preference is to avoid versions in their bugfix phase, the most current version that fits that criteria is 3.12. Version 3.13 would be viable with the same considerations driving version selection by the end of 2026, and 3.14, expected to be released in October 2025, would be viable by the end of 2027.