#[new] and #[classmethod]

[adriangb]

As far as I can tell, #[new] has to be a static method. It's a classmethod in Python, could it be made the same in PyO3? Context: I'd like to get the class name as seen by Python for the failure case of calling new.

[davidhewitt]

This seems like a reasonable thing to support, I think we could just allow #[new] and #[classmethod] attributes to be combined? Or we could have #[new(classmethod)]?

The implementation might need a bit of refactoring to make it work, the relevant code is here:

pyo3/pyo3-macros-backend/src/method.rs

Line 504 in 77fc6e6

subtype: *mut _pyo3::ffi::PyTypeObject,

subtype is exactly the cls which you'd want PyO3 to forward into the function. To enable that I think we'd need to carry extra information around which would probably require a bit of reworking of the macros. I'll try to see if I can get this done for 0.19, also PRs to help in this regard much appreciated 😄

[adriangb]

Thanks David! No promises but if I find some extra time I'll take a look at implementing it. I've never touched unsafe Rust though...

[birkenfeld]

In the case of PyO3, it's mostly unsafe due to FFI interaction with the C API. So if you know how to program extensions in C, you'll be alright.

[adriangb]

So if you know how to program extensions in C, you'll be alright.

😰