Extracting and matching Python Error in Rust

[MohamedAbdeen21]

[I'm relatively new to Rust, keep that in mind]

I want to extract the Python Error class (KeyError, TypeError,...) from PyErr.

This is what I'm using at the moment

e.to_string().split_once(":").unwrap().0

It works, but feels a little hacky and wanted to see if there's a better approach.

When I debug the entire PyErr, I can see that it already has a field for it

pyo3_runtime.PanicException: PyErr { type: <class 'KeyError'>, value: KeyError('value2'), traceback: Some(<traceback object at 0x7f6518d38980>) }

I'm aware of the is_instance_of method, but is there a way without passing the Py token?

[adamreichold]

I'm aware of the is_instance_of method, but is there a way without passing the Py token?

You definitely need a GIL token, but it should be easy to come by. Either you need to wrap your call to is_instance_of using with_gil, e.g.

fn is_key_error(err: &PyErr) -> bool {
    Python::with_gil(|py| {
        err.is_instance_of::<PyKeyError>(py)
    })
}

or better yet, you just add py: Python as an argument to your #[pyfunction] or #[pymethod] and PyO3 will provide you with a token. (The GIL is already held when PyO3 calls your function or method, hence we can just pass on the token if you request it.)

[MohamedAbdeen21]

I was looking for a way without the token. I totally forgot about the Py token provided for pymethods, I guess this can make things a bit easier.