Why we do not store information about python implementation in Pipfile or pyproject.toml?

As far as I know we do not store in metadata this information. Maybe we should change that, in my current project I want to force using only PyPy.

Very interesting question!

I did some searching, though it’s a bit hard to find good search terms, and I wasn’t able to find any discussion of this.

The answer to “why” might simply be that no one has thought of or asked for this feature.

For a library, why would you want to block people using other Python implementations from using it? For a script (or application), why not just put the interpreter to use into the shebang line?

I guess I’m not seeing why this would ever be useful. Maybe you can explain why it matters to you that your users have to use PyPy?