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ImportError: No module named rosmsg

asked 2019-06-17 04:34:50 -0500

aitazhixin gravatar image

When i install ros-melodic on machine 18.04.02, firstly installed catkin by aptitude. Installing catkin will auto install python-rosmsg, python-roslib, ..., etc. However, if then i install ros-melodic-desktop-full, catkin, python-rosmsg, python-roslib, etc. will be autoly removed. This results that i cannot use rosmsg. it will let "ImportError: No module named rosmsg". How can i install ros-melodic and catkin?

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answered 2019-06-17 19:55:30 -0500

aitazhixin gravatar image

i had resolve this problem. its reason is i set "export PATH=...." not "export PATH=${PATH}:...".

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Are you manually modifying your PATH for ROS? Or, is this related to something else?

jayess gravatar imagejayess ( 2019-06-17 20:20:48 -0500 )edit

If you're happy, we're happy, but know that you are mixing packages from different sources and that is not recommended.

gvdhoorn gravatar imagegvdhoorn ( 2019-06-18 01:11:46 -0500 )edit
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answered 2019-06-17 04:56:01 -0500

gvdhoorn gravatar image

When i install ros-melodic on machine 18.04.02, firstly installed catkin by aptitude. Installing catkin will auto install python-rosmsg, python-roslib, ..., etc.

You haven't actually installed Melodic, but an upstreamed version of some of the packages.

Please refer to wiki/UpstreamPackages for more information.

A clear indication is the name of the package: in ROS Melodic, the package would be called ros-melodic-catkin, not catkin.

However, if then i install ros-melodic-desktop-full, catkin, python-rosmsg, python-roslib, etc. will be autoly removed.

yes, and the reason is that those packages (ie: "catkin, python-rosmsg, python-roslib, etc.") are not compatible with ros-melodic-desktop-full, so apt will have to remove them.

(compatibility can actually not be guaranteed, it's not that they are inherently incompatible, but the end result is the same)

You'll want to remove the packages that you installed earlier and then do a proper install of ros-melodic-desktop-full.

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Asked: 2019-06-17 04:34:50 -0500

Seen: 32 times

Last updated: Jun 17