ImportError: No module named my_package.msg

Question

Hi I have created a package, that contains custom messages. They seem to be compiled correctly. Because I can call

rosmsg package my_package

and get

my_package/Collision

which is correct. But when I try to run a python script that depends on this message like:

from my_package.msg import Collision

I get:

ImportError: No module named my_package.msg

Do you have any Ideas what I am doing wrong?

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Some additional Info:

export | grep ROS
declare -x ROS
declare -x ROS_DISTRO="hydro"
declare -x ROS_ETC_DIR="/opt/ros/hydro/etc/ros"
declare -x ROS_MASTER_URI="http://localhost:11311"
declare -x ROS_PACKAGE_PATH="/home/aub-ch/ros/hydro_ws/src:/home/aub-ch/ros/hydro_mynavigationtest/src:/opt/ros/hydro/share:/opt/ros/hydro/stacks"
declare -x ROS_ROOT="/opt/ros/hydro/share/ros"
declare -x ROS_TEST_RESULTS_DIR="/home/aub-ch/ros/hydro_mynavigationtest/build/test_results"

and

echo $PYTHONPATH 
/home/aub-ch/ros/hydro_mynavigationtest/devel/lib/python2.7/dist-packages:/opt/ros/hydro/lib/python2.7/dist-packages

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Originally posted by ct2034 on ROS Answers with karma: 862 on 2014-06-16

Post score: 0

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Original comments

Comment by ct2034 on 2014-06-16:
For clarification: I have set the my_package as dependency in both CMakeLists.txt and package.xml of the package using the message.

Comment by ct2034 on 2014-06-24:
Hi al-dev. I added the data. Do I have to add the oder path to the PYTHONPATH as well?

Answer 1

I have a solution.

The package with the message I used was in the folder /home/aub-ch/ros/hydro_ws/src which was added to the ROS_PACKAGE_PATH. But as I used it in another catkin workspace and it was not added to the PYTHONPATH as al-dev pointed out. This was because I edited the ROS_PACKAGE_PATH myself instead of calling source devel/setup.bash
but ->

The PYTHONPATH must include this subpath of a workspace devel/lib/python2.7/dist-packages if you want to use messages out of it.
Thanks for your help!

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Originally posted by ct2034 with karma: 862 on 2014-06-24

This answer was ACCEPTED on the original site

Post score: 1

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Original comments

Comment by ct2034 on 2014-06-24:
this is correct. but i can (again) due to my karma not mark it.

Comment by antonio on 2015-11-18:
I am not sure I understand if you are suggesting a fix. Should one modify the PYTHONPATH variable to fix the problem? And if so, how should PYTHONPATH be modified?