What's the best way to set arguments in rust for List[str]

[sun-rs]

Assume there is a python func:

def string_func(codes: List[str] | None):
    my_rust_func(codes)

In rust side with pyo3, my_rust_func could accept Option<vec<&str>> or Option<vec<String>>. What's the difference between these two and which is better?

Thank you!!

[davidhewitt]

You also have Option<&PyList>. I would describe it like this:

• Option<&PyList> does no type checking on the contents, so will be fastest argument to accept but you will have to accept performance cost and fallibility later when you get items from this list and need to check if they are strings.
• Option<Vec<&str>> has checked all contents and placed them into a Rust Vec. This is a much more expensive task than just accepting &PyList, but you are now free to work with this data purely using Rust algorithms.
• Option<Vec<String>> is the same but now you've also copied all the text data into new String structures. This is more expensive again, but helpful if you need to keep ownership of the text data after the #[pyfunction] ends.

[sun-rs]

Thanks for reply! So if I need to iter this List[str] and get each of them to check if this str key is in a hashmap in rust function, the fastest argument Option<&PyList> maybe slow in the extract part? And also Option<Vec<String>> is even slower than Option<Vec<&str>>?

[davidhewitt]

Yes, that sounds like a reasonable summary.