How to implement rust-cpython as_object() and into_object()?

Question

I am trying to implement the trait PythonObject for a custom type.

impl PythonObject for PyTerm {
    #[inline]
    fn as_object(&self) -> &PyObject {
        //???
    }

    #[inline]
    fn into_object(self) -> PyObject {
        //???
    }

    #[inline]
    unsafe fn unchecked_downcast_from(o: PyObject) -> PyTerm {
        std::mem::transmute(o)
    }

    #[inline]
    unsafe fn unchecked_downcast_borrow_from(o: &PyObject) -> &PyTerm {
        std::mem::transmute(o)
    }
}

PyTerm is defined as a custom struct:

struct PyTerm {
    // not important fields
}

Tangentially related, but PyO3 is considered to be a go-to crate for Python interop. — HJVT
– HJVT, Commented Dec 30, 2020 at 18:00

MaxV · Accepted Answer · 2020-12-30 18:21:07Z

1

You may be interested in cpython::pyobject_newtype! (sources).

It looks like the macros is a blessed way to define PythonObjects.

answered Dec 30, 2020 at 18:21

MaxV

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1 Comment

Quonux Over a year ago

This didn't work because it complained that the field 0 is not defined. I suspect that they only used it for something internal. I've migrated to using PyO3, because it seems to work there pyo3.rs/v0.2.7/class.html and because it seems to be more usable and up-to-date.

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