How to define submodule in different files?

[ryansun96]

I'm following the submodule tutorial in the official doc, however I want to define my submodule in its own file:

src/lib.rs

use pyo3::prelude::*;

#[pymodule]
mod parent_module {
    #[pymodule_export]
    use super::child_module;
}

#[pymodule]
mod child_module;

src/child_module.rs

    #[pymodule_export]
    use func;

#[pyfunction]
fn func() -> String {
    "func".to_string()
}
}

If I do it this way, the compiler complains that " #[pymodule] can only be used on inline modules". If I remove #[pymodule] from above mod child_module, the compiler complains "cannot find value _PYO3_DEF in module child_module". Besides, the compiler complains " the name func is defined multiple times". Do I still need the use statement?

How can I define child_module in its own file?

[davidhewitt]

in src/child_module.rs you need to have an inline module

#[pymodule(name = "child_module")]
pub mod module {
    #[pyfunction]
    fn func() -> String {
        "func".to_string()
    }
}

... and then use super::child_module_module is the thing to export.