Discuss: PEP 827 – Type Manipulation

[NickCrews]

FRom the abstract of https://peps.python.org/pep-0827/:

We propose adding powerful type-level introspection and construction facilities to Python’s type system. This design is inspired largely by TypeScript’s conditional and mapped types, but is adapted to the distinct semantics and constraints of Python’s typing model.

From the bird’s-eye view, this proposal aims to:

• introduce new primitives in the typing module;
• broaden the annotation syntax supported by static type checkers, without requiring changes to Python’s grammar;
• ensure that the new type-level machinery benefits both static type checkers and frameworks that rely on runtime type introspection.

I wanted to make there be a discussion here in ibis, because I think this would really affect how we could type our APIs for users. For example, I think we could then actually track the schema of a table throughout processing, eg so we can error if the user tries to access a column that doesn't exist.

In general I would like such a feature to exist in python's typing. But I haven't read the proposal in much detail, so I don't have specific critiques of it. But if you have thoughts, please chime in here!

[JonAnCla]

Hey Nick thanks for mentioning this pep which I agree is useful for ibis and several other libraries my team uses that involve schema-like classes and operations on those. Assuming others agree wrt ibis, would your thoughts be to check for any gaps in the proposal vs needs in ibis, and vice support in the comments for the pep?