Why is my poetry virtualenv using the system python instead of the pyenv python that I set?

Question

I've recently installed both Pyenv and Poetry and want to create a new Python 3.8 project. I've set both the global and local versions of python to 3.8.1 using the appropriate Pyenv commands (pyenv global 3.8.1 for example). When I run pyenv version in my terminal the output is 3.8.1. as expected.

Now, the problem is that when I create a new python project with Poetry (poetry new my-project), the generated pyproject.toml file creates a project with python 2.7:

[tool.poetry]
name = "my-project"
version = "0.1.0"
description = ""
authors = ["user <user@email.com>"]

[tool.poetry.dependencies]
python = "^2.7"

[tool.poetry.dev-dependencies]
pytest = "^4.6"

[build-system]
requires = ["poetry>=0.12"]
build-backend = "poetry.masonry.api"

It seems that Poetry defaults back to the system version of Python. How do I change this so that it uses the version installed with Pyenv?

Edit

I'm using MacOS, which comes bundled with Python 2.7. I think that might be causing some of the issues here. I've reinstalled Python 3.8 again with Pyenv, but when I hit Poetry install I get the following error:

The currently activated Python version 2.7.16 is not supported by the project (^3.8).
Trying to find and use a compatible version.

[NoCompatiblePythonVersionFound]
Poetry was unable to find a compatible version. If you have one, you can explicitly use it via the "env use" command. 

Should I create an environment explicitly for the project using Pyenv or should the project be able to access the correct Python version after running pyenv local 3.8.1.? When I do the latter, nothing changes and I still get the same errors.

Answer 1

The issue arises because Poetry defaults to using the system Python rather than the Python versions installed via Pyenv. This behavior is due to how the Poetry installation process works. During installation, the script first creates a virtual environment using the system Python and then installs Poetry within that virtual environment using pip. As a result, Poetry defaults to the system Python.

You can confirm this by installing Poetry after setting up your Python versions with Pyenv. If the system Python is already configured to point to the version installed by Pyenv, Poetry will automatically use that Python version as its default.

You can check which Python is used by Poetry during installation, and which one is used in virtual environment, using:

Command poetry debug info

Output

Poetry
Version: 1.8.3
Python:  3.10.14 # python used during installation or by default referenced python

Virtualenv
Python:         3.12.7 # python used in virtual env
Implementation: CPython

To ensure that Poetry is able to use the python versions installed using pyenv, and for it to be able to find the compatible version of python as mentioned in pyproject.toml, you need to make sure that atleast the python that you want to use is set as default python in pyenv maintained python versions. So, you need to run something like pyenv global 2.7 3.8 3.10. This will set all these python's as default. This also allows poetry to find the compatible version of python when creating virtual environments and managing dependencies.

Also, you can first instruct Poetry to use your desired Python version by running poetry env use <python_version>.

Answer 2

I had the same issue where Poetry wasn't using the Python version I set with pyenv local x.y.z. Here's the solution to ensure Poetry uses the active pyenv version:

poetry env use $(pyenv which python)

Note: this solution will work until you change the active pyenv Python version using pyenv local.

Answer 3

If you installed Poetry with pipx

Things are a bit different if you installed and manage Poetry using pipx.

NOTE: Below replace the python312 command below with whatever will run the newest python, such as py or py -3.12 on windows for v3.12, similarly, replace python37 with whatever runs your older python version.

Here's my recommendation in this case:

1. Install pipx for the newest python:
   • python312 -m pip install --user pipx
   • At this point pipx will be installed to both your old and new python user folders.
2. Run pipx with list command to see what is installed. All prior installations with the old python version should still be there. The list command will tell you what Python version they were installed with. If you use the alternate way of running pipx as a module, you can force it to run with any version of python:
   • python312 -m pipx list
3. Uninstall the current poetry
   • python312 -m pipx uninstall poetry
4. Now use the newer python and pipx to install specific Python versions of poetry, using the --suffix flag to change the name of the installed file:
   • python37 -m pipx install --suffix 37 poetry
     • This will create a poetry37 entry
   • python312 -m pipx install --suffix 312 poetry
     • This will create a poetry312 entry

Although, personally, I made the poetry 3.12 version just poetry and then used poetry37 for the older python 3.7 version. Now I will run most things going forward with just poetry, but for 3.7 specific tasks I can use poetry37.

In addition, I changed the path to point to the Python 3.12 Scripts folder instead of 3.7 so the newer version of pipx could run directly at the command line without python -m pipx

Answer 4

For anyone not using the venv and came looking for the answer on making poetry use specific version of python : Upgrade pip to latest version python3.x -m pip install --upgrade pip and then install poetry for that python version python3.x -m pip install poetry

Answer 5

First I manually modified pyproject.toml and set

[tool.poetry.dependencies]
python = "^3.11.4"

Later in CLI

To deactivate the virtual env:

exit

To remove the virtual env

# rm -rf <path_to_virtual_env> 
# in my case:
rm -rf .venv

To set the local Python version (sets .python-version file)

pyenv local 3.11.4

To change Poetry env's Python version (TBH this might be the only command you need):

poetry env use 3.11.4

To activate a new virtual env:

poetry shell

And you should be all good to go. Check Python version with:

python -V

Answer 6

in my case i was running poetry via python version installed in homebrew but i tried to connect it to pyenv's python version. (since it is installed via pip i guess....)

I detected it by running:

$ where poetry

$ /opt/homebrew/bin/poetry

what worked is to remove it and install poetry again via pip in the desired version and use it the same way:

pyenv shell python3.11
python -m pip install poetry
python -m poetry install

Answer 7

My solution to this.

First of all see the situation with this command

poetry env list

If you have an output like this: project_name-QI_LjVaV-py3.9 (Activated)

you may want to get rid of this env.

So you do the "deactivation" first:

deactivate

and then the "remove" after :

poetry env remove project_name-QI_LjVaV-py3.9

Now the same command:

poetry env list

should return nothing.

Then you do:

which python3

and, if the version is ok, you use this same exact output of the path of python, to tell to poetry (Example):

poetry env use /usr/bin/python3

Do again

poetry env info 

to be sure that is using the version of the python you want.

You can continue with

poetry install

Answer 8

try re-installing poetry again

pip uninstall poetry
pip install poetry

Answer 9

In my case, I had to delete and recreate the virtualenv used by poetry. This is because I added the python version restrictions (e.g. python = ">=3.6.2 <3.7") after creating the virtualenv.

Steps

• Delete the original one: run poetry env remove myApp-XkghI9p6-py3.6
• Run any poetry step, to create it, or run poetry shell, and confirm poetry run python --version is the correct version.

Answer 10

you can specify an explicit python executable for poetry using

poetry env use <path to python executable>

This worked for me.

Answer 11

On my machine I was able to fix the "currently activated Python version is not supported by the project" error by reinstalling Poetry:

curl -sSL https://install.python-poetry.org | python3 - --uninstall
curl -sSL https://install.python-poetry.org | python3 -

After that,poetry was able to find the correct version installed by pyenv.

Answer 12

What worked for me was to run python3.8 -m poetry install.

Answer 13

You can remove the python version from pyproject.toml file and then run Poetry install

Answer 14

In my case, the environment was messed up in some way that poetry failed to activate the virtualenv properly.

Try using a different shell: perhaps, sh, or zsh. If everything works in that shell, this proves that your environment is as messed up as mine was :)

Use this command in both shells:

$ env

and try to spot the difference

Answer 15

Even though this issue has been resolved, I am writing this for somebody who comes across this problem again. After all attempts my python -V always resulted in 2.7 and no discussions mentioned running pyenv shell (surprising to me!) Adding pyenv to path

$ echo -e 'if command -v pyenv 1>/dev/null 2>&1; then\n eval "$(pyenv init -)"\nfi' >> ~/.bash_profile

In my case I had to add it to .bashrc and not bash_profile. https://ggkbase-help.berkeley.edu/how-to/install-pyenv/

Worked!

Answer 16

Alright, I figured the problem. A little embarrassingly, I had not run pyenv shell 3.8.1 before running any of the other commands. Everything works now. Thank you all for your efforts.

Answer 17

pyproject.toml is used to define all the dependencies for your project, including the supported python version.

The line your complaining about is just saying that the versions of python supported by the project is python2.7 or greater, this is independent of what versions of python you've installed with pyenv.

python = "^2.7"

If you want to update the versions of python supported by the project you can edit the file directly and run poetry update.

---

If you want to use multiple versions of python you need to make sure poetry is using the correct dependencies for the version of python you are using. To change the specific version poetry is using you should use poetry env,

• poetry env list show the versions of python poetry can use
• poetry env use <python> switches poetry to use that version.

For instance on my machine poetry has 3 virtual environments installed and is using the one associated with python3.6:

↪ poetry env list
sipy-a9sqc5pb-py3.6 (Activated)
sipy-a9sqc5pb-py3.7
sipy-a9sqc5pb-py3.8

I'm not sure how these virtual environments with interact with the shivs used by pyenv but their docs have a section relating to it

Managing Virtual Environments

There is a pyenv plugin named pyenv-virtualenv which comes with various features to help pyenv users to manage virtual environments created by virtualenv or Anaconda. Because the activate script of those virtual environments are relying on mutating $PATH variable of user's interactive shell, it will intercept pyenv's shim style command execution hooks. We'd recommend to install pyenv-virtualenv as well if you have some plan to play with those virtual environments.