Using rosgenmsg() for ROS custom message in MATLAB 2021 generation

Hi,

I am trying to generate custom ROS messages using rosgenmsg() following the link below.

https://www.mathworks.com/help/ros/ug/ros-custom-message-support.html

However, Matlab keeps telling me

"Could not install the required python packages. "

"ros.internal.createOrgetLocalPython(); % ensure python is available"

IN addiiton, my default python version is 3.8 and I have changed it to 2.7 by using

pyenv('Version','/usr/bin/python2.7'), where /usr/bin/python2.7 is the full path of my python executable.

[Jagadeesh Konakalla]

Hi,

Looks like python environment required for MATLAB is not set properly.

Can you run the following function to recreate the python virtual environment before running rosgenmsg ?

% % Re-create Python virtual environment

pyenv('Version','/usr/bin/python2.7');

ros.internal.createOrGetLocalPython(true);

Let me know if this works.

Jagadeesh K

[Zi Huang]

Hi,

Thank you for your help.

$ /usr/bin/python2.7 --version

gives me Python 2.7.12

$/usr/bin/python2.7 -m pip --version

gives me SyntaxError: invalid syntax

ros.internal.createOrGetLocalPython(true);

gives me SyntaxError: invalid syntax

. Use pyenv function to set the path to the Python executable and retry the command.

[Zi Huang]

I actually intalled pip for python2.7 by using

sudo apt install python-pip

It seems, pip is set default for python3 now.

python -m pip --version

gives me pip 21.1.1 while

python2.7 -m pip --version

gives me error message

[Nathaniel Goldfarb]

were you able to solve your problem?

Answer 1

[Murat Belge]

Can you execute the following command on bash and tell us the output?

$ /usr/bin/python2.7 --version

$/usr/bin/python2.7 -m pip --version

It looks like the version of the pip installed is not supported by Python 2.7, hence the syntax error from the pip.