Example of the generator with yield #question

[inv2004]

Hello,

Is it possible to call some python function which uses generator (would like to create it in rust part).
What is correct way to do yield(val) from pyo3 side?

Im afraid that calling from python could affect performance significantly.
Do you have any examples (with PyIterator?)?

Thank you,

[konstin]

I don't think calling yield in rust is what you want; yield is just a syntactic sugar that will build an object with __iter__ and __next__ methods from that function. What you can do in rust is to create an object that has __iter__ and __next__ which you can pass to your python code.

[inv2004]

Unfortunately, stuck a bit:

I found one example, but it uses yield:

https://pyo3.rs/master/doc/src/pyo3/types/iterator.rs.html#157

[konstin]

I'm not really sure what you're trying to do exactly, but I suppose you could try the following

pyo3/tests/test_dunder.rs

Lines 52 to 67 in 52dfc00

	#[pyclass]
	struct Iterator {
	iter: Box<iter::Iterator<Item = i32> + Send>,
	token: PyToken,
	}
	#[pyproto]
	impl PyIterProtocol for Iterator {
	fn __iter__(&mut self) -> PyResult<Py<Iterator>> {
	Ok(self.into())
	}
	fn __next__(&mut self) -> PyResult<Option<i32>> {
	Ok(self.iter.next())
	}
	}

This will allow returning your struct to python where it can be used just like a generator.

[inv2004]

Works perfect. Thank you.

[jymchng]

Hi

Just curious if the object I wish to 'yield' is not a struct but a #[pyfunction], how should I be writing this?

[mejrs]

Can you clarify what you mean? This question doesn't really make sense.

[jymchng]

Sorry, I should have been clearer.

In python, I want to be able to do the following:

class CustomCanBeValidatedType:
    @classmethod
    def __get_validators__(cls):
       yield cls.validate

    @classmethod
    def validate(cls, v, values):
        # do some validations
        return v

Here, the PyObject that is being yielded is a PyFunction, is there a way to obtain this behavior in Rust through pyo3?

Thank you.

[mejrs]

Returning functions is not related to using yield. Your best option is to make an iterator.