Add an API for getting *all* interpreters

[Jackenmen]

Right now, there's no good way of getting a list of all interpreters in the system. This can be necessary if one wants certain interpreters to be preferred over others (e.g. search for interpreter 3.10-3.14 range, preferring newer versions over older). Also, to make it more convenient for the user, one might want to provide the user with a list of the discovered interpreters that they can choose from.

I feel I should note that it is possible to implement this today with the available public APIs, just in a somewhat hacky way, using predicate callable to populate the list of interpreters:

import os
from typing import Literal

from packaging.specifiers import SpecifierSet
from packaging.version import Version
from python_discovery import PythonInfo, get_interpreter


def get_available_interpreters(requires_python: SpecifierSet) -> list[tuple[str, Version, PythonInfo]]:
    interpreters = {}

    def _append_interpreter(info: PythonInfo) -> Literal[False]:
        version = Version(info.version_str)
        if version in requires_python:
            # realpath call is needed because get_interpreter lists
            # /usr/bin and /bin as separate even though they're the same path
            interpreters[os.path.realpath(info.executable)] = info
        return False

    get_interpreter("cpython", predicate=_append_interpreter)

    ret = [(key, *value) for key, value in interpreters.items()]
    ret.sort(key=itemgetter(1), reverse=True)
    return ret

Nonetheless, I figured it's probably worth making an issue for in case this is something you're interested in explicitly supporting.

[gaborbernat]

This gets you all cpython ones, why only those?

[Jackenmen]

This gets you all cpython ones, why only those?

It just happens that in my project (which is where that function was directly taken from), the found interpreter is used with a Python project which is only tested with CPython (+ some of its dependencies, which get pip installed into venv created with the selected interpreter, are C extensions so the chance it would work with anything else is low).

I wasn't trying to propose for the new API to have this restriction - code was simply just showing the idea of how the predicate can technically already be used to achieve this with the existing API.