[Borealid]

A venv does not actually install a different Python interpreter. It's bound to the Python version that created it. You cannot make a Python 2.7 venv using a Python 3 interpreter. You need Python 3.10 to create a Python 3.10 venv.

There are plenty of situations where the Python interpreter version matters. As a non-exhaustive list, you have libraries that compile code, non-Python languages that link to cpython, build scripts that do different things depending on wheel/setup/other-bundled-stuff, Python code that uses removed compat shims like importlib-metadata...

If you haven't run into one of those situations yet, congratulations. I've been through this already, and making a reproducible environment does require first installing a pinned version of the Python interpreter and THEN setting up a venv using that particular interpreter.

[zahlman]

> You need Python 3.10 to create a Python 3.10 venv.

Yes, but this doesn't need to cause a problem for those of us using bare-bones tooling. Speaking for myself, I just... run venv with that version of Python. Because I have a global installation of everything from 3.5 to 3.13 inclusive, plus 2.7 (just so I can verify what I post online about how things used to work in 2.x). And I never install anything to my base Python versions, because my system Python is Apt's territory and the ones I built from source are only and specifically there to make venvs with.

Compiling Python from source on Linux is about as straightforward as compiling from source ever gets, honestly. (The Python dev guide has some useful tips - https://devguide.python.org/getting-started/setup-building/i... .)

[camdenreslink]

This seems like a solved problem with pyenv which is very popular. You can also include a `.python-version` in your git repo root dir to automatically use the correct python interpreter version when in the scope of that repo.

[Borealid]

Yes. It's a solved problem for Python with pyenv. Until you want to pin a particular version of Poetry.

It's also a solved problem for Ruby with rvm, node with nvm, java with the JDK_HOME env var, Maven with mvnvm, ...

Or it's a solved problem for most every tool, programming language or not, with asdf.

[nyrikki]

Most OS's use package managers these days, expecting ANY language to not run into major problems with that is just asking for trouble.

Remember that Version SAT is NP-complete: https://research.swtch.com/version-sat

How do you expect to support violating that contract, where the OS vendor, package maintainers issue updates and security fixes, while you maintain your code, with the realization that Python releases have two years of bug fixes and three additional years of security fixes. Are you actually forced into this model or are you just adding to code debt refers and adding to the accumulation of poorly written or unmaintainable code that makes future changes even harder than they are today?

Using OS package managers helps you avoid accumulating so much code debt, making moving to newer versions the easy path actually results in better written and maintainable code.

If you just listen to depreciation warnings, and prioritize trying to stay close to the current released versions, and insisting that running on unsupported versions is an incident and not hiding it under the rug, things get better over time.

That said, the Python direct download paths are very stable.

3.13.0 being: www.python.org/downloads/release/python-3130/ 2.5.5 being: www.python.org/downloads/release/python-255/

I would still recommend creating packages from those downloads, while there are possibly better options, fpm has treated me well for well over a decade.

Looking in homebrew, which is probably one of the bigger unknowns, they have targets for everything going back to 3.8, with all major Linux distros supporting farther back and obviously VM/containers are an option there too.

  brew info --json python3 | jq -r '.[].versioned_formulae[]'
  python@3.12
  python@3.11
  python@3.10
  python@3.9
  python@3.8

I have run into the situations above, but the use of unsupported and/or end-of-life software is not something you intentionally help an organization do.

Especially with the actions by several agencies to bust EULA's

While IANAL we will see what happens in the courts, when the CISA labels something as "This dangerous practice is especially egregious in technologies accessible from the Internet"

There is a very big difference between sustainment needs and active development, one is a reality, the other could possibly be framed as "Gross negligence", invalidating any EULA protections in many parts of the country.

Obviously if you are running other peoples software the calculus of trade-offs changes.

But I have done the Python 2.7 to 3.x migration for several open source and commercial projects in the past. I can promise you that the time you waste on using 2.7 with software you control is far more expensive than updating.

If you are stuck on 2.7 on a product under active development, which has been EOL for 5 years and was warned to be going away for almost a decade prior to that...the problem you have is not with any 3rd party dependancies, the problem is with your organization.

No 3rd party vendor solution will fix those problems for you.