If you wanted, you could use anEnum here instead of aString, and then defer more of the validation to pyo3 instead of manually checking the string values below.

Thanks for your comment. I did initially try to do this with an enum. Unfortunately, to use an enum in an object that derivesFromPyObject, the enum itself has to also deriveFromPyObject, but tagging a simple enum (no variants, just tags) with#[derive(FromPyObject)] results inerror: cannot derive FromPyObject for empty structs and variants.

So this errors:

#[derive(FromPyObject)]pubenumPyInsertOperation{Insert,Overwrite,Replace,}

This might be where my pyo3 knowledge is lacking. Can you point me in the right direction on how to do this as an enum properly?

I think I usually separate out the enum but then implement theFromPyObject directly on that enum. It's simpler with better separation of concerns, I think. And if you ever need to usePyInsertOperation from multiple functions, then you can reuse the same implementation