How to add a submodule to an extension with nanobind?

Question

I want to be able to add a extension to my extension, so that I can do:

import my_ext.sub_ext

In order to split up the extension so that different sub components of the extension can be imported seperately.

This is done in Boost::python like this:

bp::object class1Module(bp::handle< (bp::borrowed(PyImport_AddModule("my_ext.sub_ext"))));
bp::scope().attr("sub_ext") = class1Module;
// set the current scope to the new sub-module
bp::scope io_scope = class1Module;
// any classes defined will now be in my_ext.sub_ext
...

How is this to be achieved in nanobind?

Answer 1

You create a submodule and then pass the handle when you wrap the object you want in this new scope:

nb::module_ m2 = m.def_submodule("sub_ext", "A submodule of 'my_ext'");
nb::class_<T>(m2, "T")
.def(nb::init<>())
.def("func", &T::func)
;

The class is then available as my_ext.sub_ext.T.