Arch Linux

sethgi

Member

Registered: 2019-07-01

Posts: 5

ROS catkin_make can't find empy (suspect some sort of path issue)

Hi all,

Sorry if this is a very newbie question, I am pretty new to Arch. It just didn't feel quite like a 'newbie corner' question.

I have ros installed on my machine (i.e. roscore works) but still can't use catkin_make (on an empty catkin_ws directory with only the required /src dir). It complains:

CMake Error at /opt/ros/melodic/share/catkin/cmake/empy.cmake:29 (message):
  Unable to find either executable 'empy' or Python module 'em'...  try
  installing the package 'python-empy'
Call Stack (most recent call first):
  /opt/ros/melodic/share/catkin/cmake/all.cmake:163 (include)
  /opt/ros/melodic/share/catkin/cmake/catkinConfig.cmake:20 (include)
  CMakeLists.txt:56 (find_package)

However pip install empy gives:

sudo pip install empy
[sudo] password for sethgi: 
Requirement already satisfied: empy in /usr/lib/python3.7/site-packages (3.3.4)

This looks to me like the issue is ROS wants python2, but I have empy for python3. I can't figure out how to fix it, or to force pip to install the python2 version.

Any help is appreciated. And again, sorry for the noob-ish question.

-Seth

Last edited by sethgi (2019-07-01 21:07:10)

joaocandre

Member

Registered: 2013-02-23

Posts: 157

Re: ROS catkin_make can't find empy (suspect some sort of path issue)

Did you install ROS from AUR or compiled from source? The problem is that catkin is either using the python2 executable or looking into the python2 directories. You either install python2 empy, or tell catkin to use python3:

catkin_make -DPYTHON_EXECUTABLE=/usr/bin/python3 -DPYTHON_INCLUDE_DIR=/usr/include/python3.7m

Last edited by joaocandre (2019-07-03 12:24:31)