In ROS2 projects, it’s often useful to store boilerplate code in a «common» package to reuse across multiple parts of your project. Your common package can be a Python package or a C++ package if you wish to be flexible with C++ and Python.

To do this, follow these steps:

1. Edit CMakeLists.txt for C++ packages: Add the following line for a submodule named your_package_name_lib:
   
   ament_python_install_package(${PROJECT_NAME}_lib)
   
   Place this line before ament_package(). This command installs the Python package located in the ${PROJECT_NAME}_lib directory, where ${PROJECT_NAME} is your project name.
   
2. Edit setup.py for Python Packages: If you prefer to handle this in a purely Python package, modify setup.py as follows:
   
from setuptools import setup

setup( name='your_project_name',
version='0.1.0',
packages=['your_project_name_lib'],
install_requires=[ # List of dependencies ]
   …)