Using Python3 modules in ROS2 packages
I developed Python3 modules with code independent from ROS. Now I want to use them in a ROS2 package, more specifically I want to import them in a ROS2 node. The node listens to a ROS topic and should use my Python modules to work with the data provided by the topic.
However I couldn't find any information on how to achieve this. At first I tried to plug my modules next to the node, but when I tried to run the node after colcon build it was unable to import the modules, because colcon build runs the script in the install directory. So I modified the data_files in setup.py with
data_files=[ ('share/ament_index/resource_index/packages', ['resource/' + package_name]), ('share/' + package_name, ['package.xml']), (os.path.join('share', package_name, 'dependencies'), glob('dependencies/*')) ],
and put my modules in the dependencies directory. Now I am unable to build the package, due to a colcon error
Starting >>> tst_mapfusion_r2pp
--- stderr: tst_mapfusion_r2pp error: cant't copy 'dependencies/fusion':
doesn't exist or not a regular file
--- Failed <<< tst_mapfusion_r2pp [0.45s, exited with code 1]
Summary: 0 packages finished [0.74s]
1 package failed: tst_mapfusion_r2pp
1 package had stderr output: tst_mapfusion_r2pp
Whereas the dependencies directory contains the sub-directories for my modules, one of them being fusion.
Where do I have to put my own python modules in order to use them inside the ROS2 package? Is it possible without shenanigans like fiddling with $PYTHONPATH?
Edit: The tree is a bit extensive and I'm not allowed to upload files or pictures (new user -.- ). So please be patient with me.
/root/ros2_ws/src/tst_mapfusion_r2pp
-build
---COLCON_IGNORE
---tst_mapfusion_r2pp
----build
-----lib
------tst_mapfusion_r2pp
-------__init__.py
-------map_fusion.py
----colcon_build.rc
----colcon_command_prefix_setup_py.sh
----colcon_command_prefix_setup_py.sh.env
----dependencies
-----fusion -> /root/ros2_ws/src/tst_mapfusion_r2pp/dependencies/fusion
-----importer -> /root/ros2_ws/src/tst_mapfusion_r2pp/dependencies/importer
-----misc -> /root/ros2_ws/src/tst_mapfusion_r2pp/dependencies/misc
-----opencv -> /root/ros2_ws/src/tst_mapfusion_r2pp/dependencies/opencv
----package.xml -> /root/ros2_ws/src/tst_mapfusion_r2pp/package.xml
----resource
-----tst_mapfusion_r2pp -> /root/ros2_ws/src/tst_mapfusion_r2pp/resource/tst_mapfusion_r2pp
----setup.cfg -> /root/ros2_ws/src/tst_mapfusion_r2pp/setup.cfg
----setup.py -> /root/ros2_ws/src/tst_mapfusion_r2pp/setup.py
----tst_mapfusion_r2pp -> /root/ros2_ws/src/tst_mapfusion_r3pp/tst_mapfusion_r2pp
----tst_mapfusion_r2pp.egg-info
-----PKG-INFO
-----SOURCES.txt
-----dependency_links.txt
-----entry_points.txt
-----requires.txt
-----top_level.txt
-----zip-safe
-dependencies
--fusion
---__pycache__
----map_fusion.cpython-38.pyc
---map_fusion.py
--importer
---__init__.py
---__pycache__
----pgmloader.cpython-38.pyc
---pgmloader
--misc
---__pycache__
----mp_misc.cpython-38.py
---mp_misc.py
--opencv
---__pycache__
----ocvfmodule.cpython-38.pyc
---ocvfmodule.py
-install
-log
-package.xml
-resource
-setup.cfg
-setup.py
-test
-tst_mapfusion_r2pp
--__init__.py
--map_fusion.py
-tst_mapfusion_r2pp.egg-info
-venv
For clarity, could you please run
tree ~/location_of_workspace/src/tst_mapfusion_r2ppand update your question with the output? It should print a tree-like structure of all the files and directories.My understanding is that the
data_filesoption is only supposed to be used for extra stuff your code needs, not code itself. I would expect you would be fine just inserting your extra modules alongside the ROS-specific stuff that gets installed by thepackagesterm insetup.py. This doesn't work?I suspect, it's for ROS-packages. I've tried to add my dependencies here, but I got:
error: package directory 'dependencies' does not exist.From my limited understanding, when writing a ROS2 node with Python;
colcon buildwill copy the ROS code in the install folder, specified by setup.cfg and, for a lack of a better term, 'register' it for ROS2 to be found as run-able. So isn't it possible to tell colcon to copy my files in the proper directory when building?colcon buildis not doing anything more than invoking setuptools to install everything into theinstall/directory, the same way callingpython setup.py installwould. The stuff listed under thepackageskeywords are simply the python packages that will be placed underinstall/, which most likely should include these extra modules you mention.In case you haven't seen it, you can understand how
setup.pyand thepackageskeyword work here: https://docs.python.org/3/distutils/s... One thing that often trips people up is remembering a python package is only defined when an__init__.pyfile is present.