19.3.1. Structuring Catkin Packages

Python Packages

Note

In the following the place holder your_package is used. For your own package replace it with the name of your Catkin package.

Most packages will be written in Python. The structure should follow the conventions proposed in REP 8. So the package structure will look like:

your_package
├── CMakeLists.txt
├── README.md
├── package.xml
├── setup.py
├── config
│   └── a_config_file.yaml
├── launch
│   ├── start_a.launch
│   └── start_b.launch
├── msg
│   └── message_file.msg
├── nodes
│   ├── cool_node
│   └── also_quite_okay_node
├── scripts
│       └── script_that_is_not_a_node.py
├── src
│   └── your_package
│       ├── __init__.py
│       ├── module_a.py
│       └── module_b.py
└── srv
    └── servie_file.srv

config

Contains configuration parameters stored in .yaml files.

launch

Contains your launch files.

msg

Contains the definitions of your package’s custom messages.

nodes

Contains executable Python scripts. To be consistent with C++ executables omit the .py.

src

Contains a Python package. This has to have the same name as your Catkin package.

srv

Contains definitions of your package’s custom services.

There is no need to have the full directory structure if directories would be empty. So for example if your package does not have any services or messages, just omit the srv or msg directory respectively.

The Python modules inside src/your_package can be reused by other Python scripts via import your_package.module_a and are available for all your other Catkin packages aswell.

If your package has the src/your_package directory make sure, your CMakeLists.txt contains the line

catkin_python_setup()

and your package has a setup.py that looks like

from distutils.core import setup
from catkin_pkg.python_setup import generate_distutils_setup

setup_args = generate_distutils_setup(
    packages=["your_package"],
    package_dir={"": "src"},
)

setup(**setup_args)

Note

Replace your_package in packages=["your_package"] with your actual package name.

Also keep the hint in REP 8 in mind:

NOTE: we strive to keep ROS-specific code separate from reusable, generic code. The separation of ‘node files’ and files you place in src/packagename helps encourage this.