Handling of setup.py

If your ROS package contains python modules and scripts to install, you need to define the installation process and a way to make the scripts accessible in the develspace. The python ecosystem defines installation standards in the distutils or setuputils libraries. With those libraries, packages define the installation files in a file called setup.py in the project root. The setup.py file uses Python to describe the Python content of the stack.

Catkin allows you to specify the installation of your python files in this setup.py and reuse some of the information in your CMakeLists.txt.

You can do so by including the line:


in the CMakeLists.txt of your project.

catkin will execute setup.py with a hot-patched version of distutils or setuptools to read the arguments to set up the devel space, and execute setup.py with suitable arguments to install to the catkin install space under CMAKE_INSTALL_PREFIX.

This means that if you execute your setup.py using:

# python setup.py install

manually, that would install to a different location, and you would have multiple installed versions. Python will decide at runtime which one to use based on your PYTHONPATH environment variable, and it may pick the one you expect it to pick, but we recommend against having multiple installed versions in the first place. Using setup.py to create a pypi package of your catkin package currently has no support for ROS messages and services, and core ROS libraries (e.g. rospy) are not available on pypi, so this using setup.py for pypi is not very useful for ROS nodes.

For the develspace, the following setup.py arguments to setup() will be used by catkin:

from setuptools import setup

    package_dir={'': 'src'}

This creates relays for all scripts listed in scripts to a folder in devel space where they can be found and executed, and also relay packages for any package listed in packages. A relay package is a folder with an __init__.py folder and nothing else. Importing this folder in python will execute the contents of __init__.py, which will in turn import the original python modules in the folder in the sourcespace using the python exec() function.

The version will be compared to that declared in package.xml, and raise an error on mismatch.


If you have written non-ROS Python packages before, you have probably used the requires field in the distuils setup function. This field, however, has no meaning in ROS.

All your Python dependencies should be specified in package.xml as e.g. <run_depend>python-numpy</run_depend> (for older version 1 of package.xml) or <exec_depend>python-numpy</exec_depend> (if you use format 2 of package.xml).

Not all Python or pip packages are mapped to ROS dependencies. For a quick check, try running rosdep resolve python-mypackage or rosdep resolve python-mypackage-pip if you want to add a dependency on mypackage Python package. If these calls return error, you may want to search through the python.yaml file in rosdep for similar names. If you don’t find the requested package, you may consider creating a Pull request to add it.

Using package.xml in setup.py

Writing a setup.py file without duplicating information contained in the package.xml is possible using a catkin_pkg convenience function like this:

from setuptools import setup
from catkin_pkg.python_setup import generate_distutils_setup

d = generate_distutils_setup(
    package_dir={'': 'src'}


This will parse the package.xml and also format the fields, such that multiple authors with emails will be set nicely for setup.py, in case one distributes to pypi.


ROS Users should generally not use the scripts argument, as in ROS, executables should be executed using rosrun rather than being installed to the global bin folder. One way of installing such python scripts is to add the following to the CMakeLists.txt:

catkin_install_python(PROGRAMS scripts/myscript


See the note in previous section about the otherwise useful field requires that’s usually a part of setuptools setup. Do not use it in ROS.

Develspace limitations

For the devel space, catkin currently does not support any of the following distutils arguments:

  • py_modules
  • data_files
  • any extention module features

From setuptools, the following args are not supported for the devel space:

  • zip-safe
  • entry_points

From distribute, the following args are not supported for the devel space:

  • include_package_data
  • exclude_package_data
  • zip_safe
  • entry_points
  • setup_requires
  • namespace_packages
  • use_2to3

Those features will only work correctly for the install space.

genmsg interaction

genmsg is an external catkin package that provideslanguage bindings for ROS messages. When using the genmsg macro, ordering constraints exist, in that case you have to invoke the macros in this order:

find_package(catkin ...)