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Hello ros-users,

Ever wish your catkin package could painlessly depend on any python library under the sun?

Presenting catkin_virtualenv, a tool to define and bundle python dependencies with your catkin python packages.

We’ve been running an internal ros_buildfarm instance at Locus Robotics for almost 2 years (thanks OSRF!). One ongoing pain point was managing python package dependencies that aren’t in the Debian/Ubuntu apt repositories.

The workflow for catkin_virtualenv fits fairly well on top of the existing ROS Python-via-CMake pattern:

  1. declare a set of python requirements in requirements.txt
  2. generate a virtualenv at build time by calling CMake macro catkin_generate_virtualenv.
  3. install your python scripts via catkin_install_python as usual.
  4. add a dependency to your nosetests and rostests.

More detail is provided in the README, or see the provided test packages for toy usage examples. Behind the scenes:

  • the generated virtualenv will work transparently in devel- and install-space, and be bundled in any released debian packages.
  • package requirements will be propagated to any dependent catkin packages.
  • your python scripts will be wrapped in a loader that will work transparently with rosrun, roslaunch, and rostest.
  • adding the PYTHON3 flag to catkin_generate_virtualenv will enable your python scripts to run in python3. This mostly ‘just works’ with a lot of existing ROS components, but does have a few caveats at the moment.

One important thing to note is that the catkin_virtualenv approach does make your package artifacts noticeably ‘fatter’ due to the dependency bundling, so be wary of pulling in large dependency trees, and please continue to use rosdep+apt dependencies when possible.

Please enjoy, and I’m looking forward to feedback from anyone who finds this package useful!