How does hatch locate python versions? Can it work with pyenv?

[gerbendekkervolue]

I am stumped trying to figure out how to make hatch work with pyenv. I think I do not understand how hatch tries to locate the available python versions.

https://hatch.pypa.io/latest/config/hatch/#python-installations talks about "where to install python versions". This phrasing suggests hatch is going to install python versions on my machine, is that correctly understood? Or this this mean that I could point in this config file to my local pyenv folder and all would be fine? Am a bit hesitant to try as i do not want to mess up my pyenv directory.

https://hatch.pypa.io/latest/config/environment/advanced/#python-variables does not tell me how to ensure hatch actually finds the referred pythons.

https://hatch.pypa.io/latest/config/environment/overview/#python-version explains that one could also provide absolute paths but that would not be very helpful when setting this in pyproject.toml as I am sharing this with other developers. So hard coding a path is not a great option there.

Ideally, hatch would be able to work with pyenv by setting a config setting, providing an env variable, or any other way - but I cannot figure out how...

Any input on how to achieve this?

[jstvz]

Ideally, hatch would be able to work with pyenv by setting a config setting, providing an env variable, or any other way - but I cannot figure out how...

Any input on how to achieve this?

I can't find any references to dirs.python in the codebase outside of DirConfig (maybe it's for a planned feature? 🤷🏾‍♂️).

Hatch's default environment, virtual uses virtualenv to discover python versions, which can't see pyenv's versions:

❯ hatch env show
                  Standalone
┏━━━━━━━━━┳━━━━━━━━━┳━━━━━━━━━━━━━━┳━━━━━━━━━┓
┃ Name    ┃ Type    ┃ Dependencies ┃ Scripts ┃
┡━━━━━━━━━╇━━━━━━━━━╇━━━━━━━━━━━━━━╇━━━━━━━━━┩
│ default │ virtual │ pytest       │ cov     │
│         │         │ pytest-cov   │ no-cov  │
└─────────┴─────────┴──────────────┴─────────┘
                        Matrices
┏━━━━━━┳━━━━━━━━━┳━━━━━━━━━━━━┳━━━━━━━━━━━━━━┳━━━━━━━━━┓
┃ Name ┃ Type    ┃ Envs       ┃ Dependencies ┃ Scripts ┃
┡━━━━━━╇━━━━━━━━━╇━━━━━━━━━━━━╇━━━━━━━━━━━━━━╇━━━━━━━━━┩
│ test │ virtual │ test.py37  │ pytest       │ cov     │
│      │         │ test.py38  │ pytest-cov   │ no-cov  │
│      │         │ test.py39  │              │         │
│      │         │ test.py310 │              │         │
│      │         │ test.py311 │              │         │
└──────┴─────────┴────────────┴──────────────┴─────────┘

❯ hatch env create
Environment `default` is incompatible: cannot locate Python: 3.7

❯ hatch run test.py39:cov
Environment `test.py39` is incompatible: cannot locate Python: 39

However, setting multiple Python versions with Pyenv is possible, and allows virtualenv to discover them:

❯ pyenv local 3.8.16 3.9.16 3.10.9 3.11.1 3.7.16

❯ hatch run cov
=================================== test session starts ===================================
platform linux -- Python 3.7.16, pytest-7.2.0, pluggy-1.0.0
rootdir: /tmp/mypkg
plugins: cov-4.0.0
collected 0 items

---------- coverage: platform linux, python 3.7.16-final-0 -----------
Name                    Stmts   Miss  Cover   Missing
-----------------------------------------------------
src/mypkg/__init__.py       0      0   100%
tests/__init__.py           0      0   100%
-----------------------------------------------------
TOTAL                       0      0   100%

================================== no tests ran in 0.01s ==================================

❯ hatch run test.py311:cov
=================================== test session starts ===================================
platform linux -- Python 3.11.1, pytest-7.2.0, pluggy-1.0.0
rootdir: /tmp/mypkg
plugins: cov-4.0.0
collected 0 items


---------- coverage: platform linux, python 3.11.1-final-0 -----------
Name                    Stmts   Miss  Cover   Missing
-----------------------------------------------------
src/mypkg/__init__.py       0      0   100%
tests/__init__.py           0      0   100%
-----------------------------------------------------
TOTAL                       0      0   100%

================================== no tests ran in 0.01s ==================================

[gerbendekkervolue]

Thanks a lot for writing this up. I tried something similar before, but could not get it to work. Your answer seems to work fine for my setup:

1. hatch installed globally through pipx
2. pythons installed through pyenv

How to test whether this works for others:

• make a new hatch project using hatch new
• in the resulting folder, point to the python versions you need hatch to have available using pyenv local 3.x, 3.y as explained above
• test by running hatch run test.pyX:cov as demonstrated above.

[ofek]

FYI in the documentation I'm going to begin discouraging the use of pyenv now that we have these features:

• Implement Python management #970
• Automatically download Python distributions for virtual environments #1002