poetry: poetry env use X.Y fails on Windows

I am on the latest Poetry version.
I have searched the issues of this repo and believe that this is not a duplicate.
If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).
OS version and name: Windows 10
Poetry version: 1.0.5
Link of a Gist with the contents of your pyproject.toml file: not needed

Issue

The shortcut command poetry env use X.Y to select the environment for Python X.Y, as documented in Managing environments, is broken in Windows. One is required instead to find, copy and paste the full path to Python executable.

Note that the documentation even says “especially Windows where pyenv is not available”.

>poetry env use 3.7
'python3.7' is not recognized as an internal or external command,
operable program or batch file.

The reason is quite simple: CPython installation in Windows doesn’t provide pythonX.Y.exe, so even if you have all of them in PATH, Poetry can only find the first one. They do, however, provide registry keys with installation locations, which Poetry can use to resolve X.Y to the Python interpreter path.

This piece of code should find the path to Python, given the version number as a X.Y string:

import os
try:
    import winreg
except ImportError:
    import _winreg as winreg

def find_python_interpreter(version):
    for hkey, prefix in (
        (winreg.HKEY_CURRENT_USER, "Software"),
        (winreg.HKEY_CURRENT_USER, "Software\\WOW6432Node"),
        (winreg.HKEY_LOCAL_MACHINE, "Software"),
        (winreg.HKEY_LOCAL_MACHINE, "Software\\WOW6432Node"),
    ):
        try:
            value = winreg.QueryValue(hkey, "{}\\Python\\PythonCore\\{}\\InstallPath".format(prefix, version))
        except FileNotFoundError:
            continue
        python = os.path.join(value, "python.exe")
        if os.path.exists(python):
            return python
    return None

I have adjusted the code above to make it compatible with Python 2, but I have not tested afterwards, so please forgive any mistakes.

About this issue

Original URL
State: open
Created 4 years ago
Reactions: 20
Comments: 18 (7 by maintainers)

Most upvoted comments

In my opinion this is a bug and it’s still present on poetry 1.4.2.

The introduction page says “It is multi-platform and the goal is to make it work equally well on Linux, macOS and Windows.” It should be possible for Windows users to use the same commands.

timonviola on May 3, 2023

Same here, poetry 1.5.1, all python versions in Path, Windows10:

C:\Users\guill>py --list
 -V:3.11 *        Python 3.11 (64-bit)
 -V:3.10          Python 3.10 (64-bit)
 -V:3.9           Python 3.9 (64-bit)
 -V:3.8           Python 3.8 (64-bit)

poetry env use 3.9
Could not find the python executable python3.9

poetry env use py -3.9
The option "3" does not exist

poetry env use python3.9
Could not find the python executable python3.9

but this one is working:

poetry env use C:\Users\guill\AppData\Local\Programs\Python\Python39\python.exe
Creating virtualenv vectorbt-backtesting in C:\Users\guill\Documents\Python\vectorbt_backtesting\.venv

Guillaume-Fgt on Aug 8, 2023

#4615 was closed on the grounds that it was a duplicate.

Probably wrong. This issue is still valid. One could debate whether it is a bug or a missing feature (+ documentation bug).

radoering on Mar 12, 2023

I don’t understand why poetry env use <version> doesn’t just use py --list-paths to find the path to the desired python version on a Windows machine.

This command…:

py --list-paths

… gives this output on my machine:

-V:3.12          C:\prog\Python\Python312\python.exe
-V:3.11          C:\Prog\Python\Python311\python.exe
-V:3.10          C:\prog\Python\Python310\python.exe
-V:3.9           C:\prog\Python\Python39\python.exe
-V:3.8           C:\prog\Python\Python38\python.exe

It appears that py is a rather underrated tool. Its official name is “Python Launcher for Windows”, and it comes with every python version since 3.6 (well, every version for Windows computers, that is). It is compatible with older versions too, if just one of the newer versions is installed. I never use python anymore. I always use py followed by a version and a command, for example:

py -3.11 -m venv ./.venv

AllanHOlesenBW on Mar 1, 2024

I have exactly the same issue, its quite annoying to be honest.

interceptor on Oct 17, 2023

Which version of py are you using?

I think I am using the version, which came with Python 3.12.0. But I couldn’t find a way to make it reveal its version, and it is installed in a separate directory.

I just checked the registration database, and all my installed Python versions from 3.8 to 3.12 have the PEP 514 entries here: Computer\HKEY_CURRENT_USER\SOFTWARE\Python\PythonCore\

But I only have 3.11 and 3.12 in my path. So I wonder if Pythonfinder only uses the path, though it claims to use the registration database.

AllanHOlesenBW on Mar 4, 2024

It seems to me that for poetry env use to use py --list-paths on Windows would be a step forward. However, it is not always present, since it is not included with the builds of Python provided by the Microsoft Store packages of Python. (I think it can also always be deselected explicitly when installing Python on Windows in the usual way, but this is less significant because people probably don’t deselect it and, if they do, are likely aware that they have done so.)

EliahKagan on Mar 1, 2024

same issue here. Any progress on this one? currently on poetry 1.6.0 (Windows 11)

mandar-karhade on Jan 8, 2024

Not sure if we have to implement PEP 514 compliant searching by ourselves. It may be more sustainable to use an existing lib (e.g. pythonfinder).

radoering on Apr 11, 2022