python-roslib : Depends: catkin but it is not going to be installed

asked 2021-11-10 02:09:42 -0500

Alex2008
15 ●2 ●3 ●5

updated 2021-11-10 02:28:51 -0500

gvdhoorn
86574 ●283 ●1432 ●1054 http://cor.tudelft.nl/

When i run the command:

roslaunch turtlebot3_bringup turtlebot3_robot.launch

I get the following message:

Command 'roslaunch' not found, but can be installed with:
sudo apt install python-roslaunch

So I try this command, giving me the following message:

The following packages have unmet dependencies:
 python-roslaunch : Depends: python-roslib but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

So I try to install python-roslib, using the command:

sudo apt install python-roslib. This gives me the following error: The following packages have unmet dependencies:
 python-roslib : Depends: catkin but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

Does anybody now how I can fix this?

answered 2021-11-10 02:24:43 -0500

gvdhoorn
86574 ●283 ●1432 ●1054 http://cor.tudelft.nl/

updated 2021-11-10 02:26:07 -0500

You appear to be running into problems trying to mix wiki/UpstreamPackages and regular ROS packages.

Note how all packages you mention don't have the name of the ROS version you're using in them: python-roslaunch, python-roslib and catkin.

In ROS Melodic, the correct package names would be: ros-melodic-roslaunch, ros-melodic-roslib and ros-melodic-catkin.

You cannot mix upstream packages with packages from a ROS release (that's not entirely true, but if you're just starting out, I would probably heed the advice given on the wiki page and not attempt to do so). See the linked wiki page for more information about them, and see “upstream packages” increasingly becoming a problem for a recent-ish discussion.

But your initial problem was:

When i run the command: roslaunch turtlebot3_bringup turtlebot3_robot.launch

I get the following message: Command roslaunch not found, but can be installed with: sudo apt install python-roslaunch

did you perhaps forget to source /opt/ros/melodic/setup.bash (or the equivalent for your workspace) before trying to use roslaunch? If you don't source your ROS installation (or workspace), your shell will not be able to find roslaunch, which on Ubuntu causes it to suggest installing the python-roslaunch package.