When should you upgrade to Python 3.13?
Python 3.13 will be out October 1, 2024—but should you switch to it immediately? And if you shouldn’t upgrade just yet, when should you?
Immediately after the release, you probably didn’t want to upgrade just yet. But from December 2024 and onwards, upgrading is definitely worth trying, though it may not succeed. To understand why, we need to consider Python packaging, the software development process, and take a look at the history of past releases.
The problems with a new major Python release
As with many open source projects, Python, Python libraries, and most of the toolchain and packages mentioned in this article are based on volunteer labor. None of this should be read as a complaint towards the people doing the maintenance, they’re doing hugely valuable work, released for free and often done for free, and everything takes time. In addition, because upgrades involve so many different groups, coordination and releases take even more time.
With that in mind, let’s consider the problems with using 3.13 immediately after a release, and in the following months:
1. Incompatible packages
In some cases, the code in a library is incompatible with a new Python release. Given many Python packages are maintained by volunteers with limited free time and working independently, it just takes time for updates to percolate through the system.
To give an example, as of mid-September 2024:
- Polars didn’t support Python 3.13. Work couldn’t even start because it was blocked on rust-numpy supporting 3.13.
- rust-numpy support for 3.13 was in progress, but it needed to both switch to a newer and somewhat incompatible version of PyO3 first, and also add NumPy 2.x support.
It may be that by the time 3.13 is out all this work will be finished, but there are no guarantees. Again, not a complaint, just a reality of depending on volunteer efforts for key packages.
2. Missing binary packages
Even if the code is compatible, not all packages can be easily installed on 3.13 yet.
Typically, Python package maintainers upload compiled versions of their packages–known as “wheels”–to PyPI. When you install a package, you can just download the binary wheel and don’t need to compile it (though wheels are harder to come by if you use Alpine Linux, in which case wheels may or may not be available).
But at least for a short time after 3.13’s release, some packages won’t have wheels for Python 3.13 uploaded yet. This is less of a problem these days compared to older Python releases, as:
- Package maintainers are putting in more and more effort to shorten this window, often releasing updated packages in advance of the Python final release.
- Some packages release binary wheels using the forward-compatible “abi3” format, which means newer Python releases just work with no extra effort.
Nonetheless, there will be packages that won’t have binary wheels yet. Best case, that means installation will take a lot longer as you have to compile the code on installation. Worst case, compilation will fail because you don’t have relevant compile-time dependencies installed.
Conda support
If you’re using Conda-Forge, the Python 3.13 rollout happens pretty quickly. A lot of it is automated, one of the benefits of Conda-Forge over PyPI, so as long as the underlying packages already support 3.13, it happens pretty quickly across the whole package repository.
3. Bugs in Python
Python 3.12.0 was released in October 2023. 3.12.1 was released in December 2023, with more than 400 bugfixes.
Of course, there’s always another bug fix release in the future, but given a 12-month window between major releases, lots of new code will get written but not extensively used. Which means Python 3.13.0 can also expect a follow-up 3.13.1 release with a large number of bug fixes.
Things are getting better!
I’ve been updating this article over the years since 3.9, and the situation has gotten significantly better since then. Every release I’ve reduced the caveats, and projects have sped up their iteration cycles so they have support for newer releases even faster.
Is upgrading worth it?
Given that it takes work to upgrade—some additional testing, some tweaks to your code—it can be tempting to put off upgrading Python versions indefinitely. Why worry about incompatibilities, new versions, and what not, when you can just stick with your current version indefinitely?
The problem is that Python isn’t supported indefinitely, nor do libraries support all Python versions indefinitely; eventually you’ll stop getting security updates and bug fixes. Python 3.8 ends security updates in October 2024. 3.9 will be next, dropping security updates in October 2025.
So sooner or later you will have to upgrade. And if you’re running on a 5-year-old version of Python, switching becomes a Big Deal—you’ll often end up dealing with more significant cross-version changes in both Python and in libraries at the same time. Which makes upgrading scary.
Instead of one massive scary upgrade event every few years, it’s much safer to have a continuous, ongoing process of smaller upgrades. Whenever a new major Python version comes out, or a new major library version, wait a bit, and then switch.
The week Python 3.12 was released, you probably didn’t want to upgrade, but you certainly wanted to be using 3.11. Even if you can’t upgrade to 3.13 yet, you should try to upgrade to Python 3.12 if at all possible.
When should you switch your application to Python 3.13?
At a minimum, after a major new release you will need to wait until:
- All your libraries explicitly support the new Python release.
- All the tools you rely on explicitly support the new Python release.
Once 3.13.1 comes out in December 2024, you’ll both get the bug fixes and most packages will be updated, and it’s worth trying to upgrade. If the dependencies you require are still missing 3.13 support, keep trying again every month or two.
