Create a Python module with pybind11 and use it in another package

edit

I found a way to do it. pkg1's CMakeLists.txt should look like this:

cmake_minimum_required(VERSION 3.5)
project(pkg1)
find_package(ament_cmake REQUIRED)
find_package(pybind11 REQUIRED)

ament_python_install_package(${PROJECT_NAME})

pybind11_add_module(mymodule src/example.cpp)
install(TARGETS mymodule
  DESTINATION "${PYTHON_INSTALL_DIR}/${PROJECT_NAME}"
)

ament_package()

example.cpp:

#include <pybind11/pybind11.h>
int add(int i, int j) { return i + j; }
PYBIND11_MODULE(mymodule, m)
{
    m.def("add", &add, "A function which adds two numbers");
}

Finally, one needs to create my_workspace/src/pkg1/pkg1/__init__.py with the following content:

from pkg1.mymodule import *

After sourcing my_workspace/install/setup.sh one can start Python and do:

>>> import pkg1
>>> pkg1.add(5,3)
8