The Python runtime itself may depend on system libraries.

Python packages usually include their own bundled compiled code (either directly in the wheel, or else building an sdist will build complete libraries that end up in site-packages rather than just wrappers). A wheel for NumPy will deliver Python code that uses an included copy of OpenBLAS, even if your system already had a BLAS implementation installed.

Regardless, that has no bearing on how virtual environments work.

> I won't even bother to address in detail the insanity that you described about virtual envs, it's just Stockholm syndrome. Almost every other programming language does just fine without venvs.

You say this like you think there's something difficult or onerous about using virtual environments. There really isn't.

> Also I don't really buy that issue with the lack of portability

The use of absolute paths is the only thing preventing you from relocating venvs, including moving them to another machine on the same architecture. I know because I have done the "surgery" to relocate them.

They really do have the reason for using absolute paths that I cited. Here's someone from the Pip team saying as much a few days ago: https://discuss.python.org/t/_/96177/3 (Using a relative path in the wrapper script would of course also require a little more work to make it relative to the script rather than to the current working directory. It's worse for the activation script; I don't even know if that can be done in pure sh when the script is being sourced.)

Yes, it's different between Linux and Windows, because installers will create actual .exe wrappers (stub executables that read their own file name and then `CreateProcess` a Python process) instead of Python wrapper scripts with a shebang. They do this explicitly because of the UX that Windows users expect.

> Even for Windows there are better possibilities (symlinks are feasible, you just need admin access).

Please go survey all the people you know who write code on Windows and see how many of them have ever heard of a symlink or understand what they are. But also, giving admin rights to these Python tools all the time is annoying, and bad security practice (since they don't actually need to modify any system files).

> The sane way to do virtual envs is to have them be just... folders. No absolute paths, no activation, just have a folder and a configuration file.

A virtual environment is just a folder (hierarchy) and a configuration file. Like I said, activation is not required to use them. And the fact that certain standard tools create and expect absolute paths is not essential to what a virtual environment is. If you go in and replace the absolute paths with relative paths, you still have a virtual environment, and it still works as you'd expect - minus the tradeoffs inherent to relative paths. And like I said, there is third-party tooling that will do this for you.

Oh, I guess you object because there are actual symlinks (or copies by default on Windows) to Python in there. That's the neat thing: because you start Python from that path, you don't need a launcher. (And you also, again, don't need to activate. But you can if you want, for a UX that some prefer.) Unless by "launcher" you meant the wrapper script? Those are written to invoke the venv's Python - again, you don't need to activate. Which is why this can work:

  sudo apt install pipx
  pipx install sphinx
  sphinx-quickstart

Again, yes, the wrapper scripts would have to be a little more complex in order to make relative paths work reliably - but that's a Pip issue, not a venv issue.