Cannot return PyBytes / PyList?

[vedantroy]

I have the following:

    pub fn apply_local_change(&mut self, change: &PyAny) -> PyResult<(Py<PyAny>, PyBytes)> {
       // function implementation ...
        let bytes = *PyBytes::new(py, change.raw_bytes());
        Ok((pythonize(py, &patch)?, bytes))
    }

However, I get an error saying "the trait IntoPyCallbackOutput<_> is not implemented for Result<(pyo3::Py<PyAny>, PyBytes), PyErr>". Is there any reason this trait would not be implemented for PyBytes?

I can solve the problem by returning a Vec<u8>, but that seems less Pythonic.

Update: This seems to apply for all Py... types, i.e, I can't return a Pylist either.

[ravenexp]

I think this is because you are trying to return a Rust tuple. Maybe you could try returning a PyTuple object instead.

[davidhewitt]

Sorry for my slow response! The return type needs to be PyResult<(Py<PyAny>, &PyBytes)> or PyResult<(Py<PyAny>, Py<PyBytes>)>.

(Plain PyBytes isn't meaningful with PyO3 - it needs to be wrapped as a pointer either as &PyBytes or Py<PyBytes>. This is likely going to improve eventually with #1308.)

[davidhewitt]

Will close this as it's been a stale discussion and we'll be marking a lot of documentation changes in #3382