Use more appropriate error variants in various places across the API

[stinodego]

We often use ComputeError as a default, but we have a bunch of different error types available. Sometimes using a different error type is more appropriate, such as a DuplicateError or SchemaError.

On the Python side, there is also the occasional ValueError that should be a TypeError and similar.

Please comment here with any errors that you know/feel are incorrect (ideally include a code example that triggers the error), and I will update #15030 accordingly. Then this can be updated in one breaking PR.

[s-banach]

Can you tell me how to import exceptions in a way the type-checker will understand?
I guess they're imported from polars.polars, but the type checker is greyed-out on polars.polars.

[stinodego]

Can you tell me how to import exceptions in a way the type-checker will understand? I guess they're imported from polars.polars, but the type checker is greyed-out on polars.polars.

They are available on top-level, so you can use pl.ComputeError. Or you can from polars.exceptions import ComputeError and then use it.