Runtime Types in pyo3

[vkobinski]

I want to implement a match case for a Type that is parsed at Runtime, i just need to match to the right case when the match is executed, I achieved a state where I can desestructure the arguments, but I can't make the right case be matched.

My code:
https://github.com/vkobinski/benda-main/blob/1405203f697ba3232160943cf4b36719134e432b/crates/benda/src/types/book.rs#L164

My problem:
All the types i create at runtime are of the type builtins.Ctr, i just need to change this type for the match case.

[davidhewitt]

Can you reduced this down to a more contained example of the problem? I took a quick look at your link but there's a lot there and it's not immediately clear to me what you're asking.

[davidhewitt]

Can you write out in short form the match you're trying to implement? Maybe I can offer suggestions then.

[vkobinski]

Do you know how Python compares an object with a Type? I tried changing the PyTypeObject name and it continued to be matched.

[vkobinski]

my_list = book.adts.List.Cons(10, book.adts.List.Nil())

while my_list:
    match my_list:
        case book.adts.List.tCons(value, tail):
            print(value)
            lista = tail
        case book.adts.List.tNil():
            print("End")
            break

And the type is returned by this PyClass:

#[pyclass(name = "Ctrs")]
#[derive(Clone, Debug, Default)]
pub struct Ctrs {
    fields: IndexMap<String, Ctr>,
}

#[pymethods]
impl Ctrs {
    // TODO: Return Type or Constructor

    fn __getattr__(&self, object: Bound<PyAny>) -> PyResult<pyo3::PyObject> {
        let py = object.py();

        if object.to_string().starts_with("t") {
            let b_name = object.to_string();
            let name = b_name.strip_prefix("t").unwrap();

            let type_obj = Ctr::type_object_bound(py);

            return Ok(type_obj.to_object(py));
        }

        if let Some(val) = self.fields.get(&object.to_string()) {
            Ok(Py::new(py, val.clone()).unwrap().into_any())
        } else {
            new_err(format!("Could not find attr {}", object))
        }
    }
}

But all objects like this are Ctr, i just need to make List.Cons not map to Ctr.

[davidhewitt]

I think probably you want to use object.is_instance(cons)? - Where you can use py.import to load the Python module and get the Cons type.

[vkobinski]

I'm trying to modify isinstace for my Ctr PyClass, but I'm not able to find what method Python is calling on my object. Pretty hard.

[vkobinski]

while my_list:
    match my_list.name:
        case book.adts.List.Cons.name:
            print(my_list.head)
            my_list = my_list.tail
        case book.adts.List.Nil.name:
            print("End")
            break

My solution for now, can't make the PyType work.