[issue42041] venv subprocess call to python resolves to wrong interpreter

[Paul Moore]

Paul Moore <p.f.moore at gmail.com> added the comment:

> This is still true, though, as much as it's ever been.

But it's *not*, if I understand the problem here. Windows resolves a bare "python" command by searching the directory containing the running executable first. I would reasonably assume that if I type

    path/to/venv/scripts/python.exe foo.py

then the "running executable" is "path/to/venv/scripts/python.exe", and so the path containing the running executable is "path/to/venv/scripts", so a search for "python" will locate "path/to/venv/scripts/python.exe", because that's how Windows path search rules work. The problem is that that exe is a redirector, and the script is *actually* being run by the system Python.

Of course, the assumption I made is flawed, because there's never been anything saying that a program called "python.exe" can't do anything it likes in the process of running a script, including redirecting. But it's been the case for a long time, and IMO the introduction of the redirector counts as a user-visible behaviour change, and we should therefore explicitly point it out.

I really don't see why you are so reluctant to include this. I'm not asking that we guarantee any behaviour, or that we commit ourselves to anything. Just that we note that people ought not to be making a specific assumption (which it appears from this issue, people *have* been making).

> we could phrase it more positively

Cool, I'll update the PR to add this statement or something similar to the subprocess docs in the next couple of days.

I'm not going to fight to keep the comments in the venv documentation. I'm disappointed, and I feel like we'll end up with people relying on *more* of the implementation details because we're keeping things vague, but I have more important things to debate, so I'll drop this :-)

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<https://bugs.python.org/issue42041>
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