Hello, a coworker of mine is running into some trouble when using Pants. In our

pants.toml

file, we have the following:

[python]
interpreter_constraints = ["CPython==3.9.*"]

However, when he runs Pants commands, he sees the following line:

Bootstrapping Pants using /usr/local/bin/python3.7

This is problematic because we use Python 3.9 features, which is causing his runtime to fail. What is the reason that Python 3.7 is being used here?

Pants uses Python to run itself. Your first config is the ICs Pants should use to run your code. It should be OK (in most cases) that Pants runs itself with 3.7, but your code with 3.9. What's the error? In a plugin?

Yup, in a plugin! I do the following in there

from typing import Final

Ah yeah, might want to do

from __future__ import annotations

and then also

if TYPECHECKING: from typing import Final

Awesome, I think that fixes it. Thanks Josh!

Ah, right, Pants can run on 3.7 but run your code on 3.9, no problem (think of that 3.7 as an implementation detail of Pants). The only time this isn't quite true is in-repo Pants plugins.

https://www.pantsbuild.org/docs/options#pantsrc-file

pants.rc

is definitely your friend on this one. My Xcode python get's periodically pulled in for some reason. At least it used to....