Error in building custom ros messages

Hello, i am trying to communicate with ros by using my custom messages. I'm currently using ROS1 Melodic. I saw that there is a function called rosgenmsgs and i tried to build my custom messages with

rosgenmsg("/home/msezer/catkin_ws/src/cust_msgs")

However, i got the following error,

Error using ros.internal.createOrGetLocalPython
Could not find Python version 3.9 on your system. Use pyenv function to set the path to the Python 3.9 executable.

Then i installed the Python 3.9 and gave the executable path by using

pyenv('Version','/usr/bin/python3.9')

After calling the function rosgenmsg, i get the following error.

Error using ros.internal.createOrGetLocalPython
chmod: cannot access '/home/msezer/.matlab/R2022a/ros1/glnxa64/venv/bin/activate': No such file or directory
Error in rosgenmsg (line 88)
ros.internal.createOrGetLocalPython(); %ensure python is available

I've already check the path and there is no activate folder or file. I use Ubuntu 18.04. What could be the reason for this problem?

Thank you

Answer 1

[Alexandre Lamarre]

I had the same problem since I update Matlab to 2022a. It seem that you have to create a Python venv environment in your ‘/home/msezer/.matlab/R2022a/ros1/glnxa64/venv/’ folder.

To achieve that, navigate to your ‘/home/msezer/.matlab/R2022a/ros1/glnxa64/venv/’ folder and delete everything in it. Then in a terminal, create a python venv environment with the following command:

$ python3 -m venv [Directory of your venv folder]

It will create the environment and you should be able to generate yours custom ROS message. It worked for me.

Regard,

Alexandre

[Mustafa Sezer]

Hello, thank you for the answer. I tried the solution, however it did not solve my problem. I tried something similar with a small difference. I deleted the files under the venv folder and in a terminal i used the command

$ sudo apt install python3.9 python3.9-venv python3.9-dev

Then, i created the virtual environment with

$ python3.9 -m venv [Directory of your venv folder]

It solved my problem. Thank you.

[Pin-Hsuan Huang]

Hello Mustafa Sezer, thank you for your answer. I had the same problem and it is solved just as you suggested. Thank you very much!

[Cristian Chitiva]

thank you, also works for me

Answer 2

[Josh Chen]

Hello Mustafa,

Looking at the error message, it seems that the python virtual environment was not been created properly. Could you please try to create the python virtual environment again with the following command and see if that works?

>> ros.internal.createOrGetLocalPython(true);

Thanks,

Josh

[Mustafa Sezer]

I tried it but i still got an error. I could solve my issue with the solution above. Thank you for your time