How to use poetry to support multiple versions of python? Why can't poetry figure what version of scipy works with python 3.7?

[mforbes]

Here is a simple use case: I would like a project to support python 3.7 through 3.11 with scipy. How should I construct the dependencies? It seems like a tool such a poetry should help, but I don't see how to get it to help.

I would like to start with python = ">=3.7,<3.12":

pyproject.toml

# pyproject.toml
[tool.poetry]
name = "test-scipy"
version = "0.1.0"
description = ""
authors = []

[tool.poetry.dependencies]
python = ">=3.7,<3.12"

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

Then add scipy:

poetry add scipy

$ poetry add scipy
Using version ^1.10.1 for scipy

Updating dependencies
Resolving dependencies... (0.0s)

The current project's Python requirement (>=3.7,<3.12) is not compatible with some of the required packages Python requirement:
  - scipy requires Python <3.12,>=3.8, so it will not be satisfied for Python >=3.7,<3.8

Because no versions of scipy match >1.10.1,<2.0.0
 and scipy (1.10.1) requires Python <3.12,>=3.8, scipy is forbidden.
So, because test-scipy depends on scipy (^1.10.1), version solving failed.

  • Check your dependencies Python requirement: The Python requirement can be specified via the `python` or `markers` properties
    
    For scipy, a possible solution would be to set the `python` property to ">=3.8,<3.12"

    https://python-poetry.org/docs/dependency-specification/#python-restricted-dependencies,
    https://python-poetry.org/docs/dependency-specification/#using-environment-markers

This fails scipy requires Python <3.12,>=3.8, so it will not be satisfied for Python >=3.7,<3.8. Perhaps requiring such a wide range is too much. How about just python 3.7?

I would like to start with python = "~=3.7.16":

pyproject.toml

# pyproject.toml
[tool.poetry]
name = "test-scipy"
version = "0.1.0"
description = ""
authors = []

[tool.poetry.dependencies]
python = "~=3.7.16"

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

$ poetry env use 3.7
$ poetry add scipy
Using version ^1.10.1 for scipy

Updating dependencies
Resolving dependencies... (0.1s)

Package operations: 2 installs, 0 updates, 0 removals

  • Installing numpy (1.24.3)
  • Installing scipy (1.10.1)

Writing lock file
(work-base) Admins-MacBook-Pro-2:scipy mforbes$ poetry add scipy

Current Python version (3.8.16) is not allowed by the project (~=3.7.16).
Please change python executable via the "env use" command.
(work-base) Admins-MacBook-Pro-2:scipy mforbes$ poetry env use 3.7
Using virtualenv: /Users/mforbes/Library/Caches/pypoetry/virtualenvs/test-scipy-0LcpY0vh-py3.7
(work-base) Admins-MacBook-Pro-2:scipy mforbes$ poetry add scipy
Using version ^1.10.1 for scipy

Updating dependencies
Resolving dependencies... (0.0s)

The current project's Python requirement (>=3.7.16,<3.8.0) is not compatible with some of the required packages Python requirement:
  - scipy requires Python <3.12,>=3.8, so it will not be satisfied for Python >=3.7.16,<3.8.0

Because no versions of scipy match >1.10.1,<2.0.0
 and scipy (1.10.1) requires Python <3.12,>=3.8, scipy is forbidden.
So, because test-scipy depends on scipy (^1.10.1), version solving failed.

  • Check your dependencies Python requirement: The Python requirement can be specified via the `python` or `markers` properties
    
    For scipy, a possible solution would be to set the `python` property to "<empty>"

    https://python-poetry.org/docs/dependency-specification/#python-restricted-dependencies,
    https://python-poetry.org/docs/dependency-specification/#using-environment-markers

Now scipy requires Python <3.12,>=3.8, so it will not be satisfied for Python >=3.7.16,<3.8.0. Why can't poetry figure out that scipy 1.7.3 supports python 3.7? I thought this type of thing was what Poetry was designed for?

For the record, something like this works. Is there some way tools like Poetry can help me figure this out without having to manually scrub through the scipy historical records?

# pyproject.toml
[tool.poetry]
name = "test-scipy"
version = "0.1.0"
description = ""
authors = []

[tool.poetry.dependencies]
python = ">=3.7,<3.12"
scipy = [
    {version = ">=1.7.3", python=">=3.7,<3.8"},
    {version = ">=1.8.1", python=">=3.8"},
    {version = ">=1.10.0", python=">=3.11"},
]

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

[radoering]

#707