venv.EnvBuilder creates inconsistent venv depending on the name of the Python executable

[EtienneMiret]

Bug report

Bug description:

Given the below create-venv.py script and several Python 3 installed in the classpath:

import sys
import venv


if __name__ == "__main__":
    venv.EnvBuilder().create(sys.argv[1])

Let’s create various venvs:

for VERSION in 3.9 3.11 3.12; do
  python$VERSION create-venv.py $VERSION-venv
  for EXEC in python python3 python$VERSION; do
    $VERSION-venv/bin/$EXEC create-venv.py $VERSION-$EXEC-venv
  done
done

And now, let’s check them:

for PYTHON in *-venv/bin/python; do
  echo "$PYTHON: $($PYTHON --version)"
done

The above loop outputs:

3.11-python3.11-venv/bin/python: Python 3.11.7
3.11-python3-venv/bin/python: Python 3.9.14
3.11-python-venv/bin/python: Python 3.9.14
3.11-venv/bin/python: Python 3.11.7
3.12-python3.12-venv/bin/python: Python 3.12.1
3.12-python3-venv/bin/python: Python 3.9.14
3.12-python-venv/bin/python: Python 3.9.14
3.12-venv/bin/python: Python 3.12.1
3.9-python3.9-venv/bin/python: Python 3.9.14
3.9-python3-venv/bin/python: Python 3.9.14
3.9-python-venv/bin/python: Python 3.9.14
3.9-venv/bin/python: Python 3.9.14

As the reader can see, Python venv’s created by python or python3 executable of a Python venv will not use the Python of this venv, and instead will use the system’s default Python (3.9 in my case).

CPython versions tested on:

3.11, 3.12

Operating systems tested on:

Linux

[FFY00]

This happens because it likely copies/symlinks the interpreters from PATH, which points to the wrong versions as the venv is not active. We could prefer to copy them from the scripts path of the running interpreter, but I am wary of that as some people might be relying on the current behavior.