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I've analyzed the error you're encountering when running the ros2 run astra_controller teleop_web_node command in your ROS2 workspace. The error message indicates a ModuleNotFoundError for the trimesh module, which is required by the urchin package used in your project. Below, I'll explain why this is happening and provide a clear, step-by-step solution to fix it.

Why You're Seeing This Error

The error occurs because the Python interpreter running the teleop_web_node script cannot find the trimesh module. Looking at the traceback:

  • The script is executed using the system Python interpreter (/usr/lib/python3.10), as seen in the paths referenced in the error (e.g., /usr/lib/python3.10/importlib).
  • However, you’re working in a virtual environment named non_ros, where trimesh is likely installed (or should be installed).

The mismatch happens because:

  • The teleop_web_node script’s shebang line (the first line of the script, starting with #!) is likely set to #!/usr/bin/python3, which points to the system Python instead of your virtual environment’s Python (/home/jammy/.venvs/non_ros/bin/python).
  • As a result, when the script tries to import trimesh, it looks in the system Python’s site-packages directory, where trimesh isn’t installed, rather than your virtual environment’s site-packages.

This explains why the error persists even after building your ROS2 workspace—building doesn’t change the interpreter used by the script.

How to Fix It

To resolve this, you need to ensure the teleop_web_node script uses the Python interpreter from your non_ros virtual environment, where trimesh is (or will be) installed. Follow these steps:

Step 1: Activate Your Virtual Environment

Make sure your non_ros virtual environment is active:

source /home/jammy/.venvs/non_ros/bin/activate

You should see (non_ros) in your terminal prompt, as in your query.

Step 2: Verify trimesh Is Installed

Check if trimesh is installed in your virtual environment:

pip show trimesh
  • If installed: You’ll see details like the version and location (e.g., /home/jammy/.venvs/non_ros/lib/python3.10/site-packages). Skip to Step 3.
  • If not installed: Install it with: 
    pip install trimesh

Step 3: Check the Script’s Shebang Line

Look at the first line of the teleop_web_node script to see which Python interpreter it uses:

head -n 1 /home/jammy/ros2_ws/install/astra_controller/lib/astra_controller/teleop_web_node

It probably says #!/usr/bin/python3, which points to the system Python. We need to update this to use your virtual environment’s Python.

Step 4: Update the Shebang Line

Modify the script to use the correct Python interpreter:

  1. Open the script in a text editor (e.g., nano): 
    nano /home/jammy/ros2_ws/install/astra_controller/lib/astra_controller/teleop_web_node
  2. Change the first line from #!/usr/bin/python3 to: 
    #!/home/jammy/.venvs/non_ros/bin/python
  3. Save the file (in nano, press Ctrl+O, then Enter, then Ctrl+X to exit).

Step 5: Test the Node

Run the node again:

ros2 run astra_controller teleop_web_node

The script should now use the virtual environment’s Python interpreter, find trimesh, and execute without the ModuleNotFoundError.

Why This Works

  • The shebang line (#!) tells the system which interpreter to use when running the script. By pointing it to /home/jammy/.venvs/non_ros/bin/python, you ensure it uses the Python from your virtual environment.
  • Since trimesh is installed in the virtual environment’s site-packages, the updated interpreter can find and import it successfully.

Additional Tips

  • Rebuilding the Workspace: If you rebuild your ROS2 workspace later (e.g., with colcon build), the shebang line might revert to the system Python. You’d need to repeat Step 4 or adjust your build process to use the virtual environment’s Python (e.g., by setting the PYTHON_EXECUTABLE variable during the build).
  • Consistency: Always activate your virtual environment and source your ROS2 workspace (source /home/jammy/ros2_ws/install/setup.bash) before running nodes to avoid similar issues.
  • Double-Check Dependencies: If you still see errors, ensure all other dependencies required by urchin or your project are installed in the non_ros environment.