Creating a Python Extension

Creating a Python-based extension is the easiest way to add new functionality to RCS, especially for hardware that already has a Python API.

Structure

A typical Python extension has the following structure:

rcs_myext/
├── pyproject.toml
├── README.md
└── src/
    └── rcs_myext/
        ├── __init__.py
        └── my_device.py

Steps

1. Create pyproject.toml: Define your package metadata and dependencies.

   [build-system]
   requires = ["setuptools>=61.0"]
   build-backend = "setuptools.build_meta"
   
   [project]
   name = "rcs_myext"
   version = "0.1.0"
   dependencies = [
       "rcs",
       # Add other dependencies here
   ]
   

2. Implement the Interface: Create your device class in src/rcs_myext/my_device.py. You should inherit from the appropriate RCS base class (e.g., Camera, Gripper) if applicable, or implement the required methods.

3. Register the Extension: If your extension needs to be discoverable by RCS (e.g., for CLI tools or automatic loading), ensure it’s installed in the same environment.

Example: USB Camera

The rcs_usb_cam extension is a good example of a pure Python extension. It wraps cv2.VideoCapture to provide a camera interface compatible with RCS.

from rcs.camera import Camera

class WebCam(Camera):
    def __init__(self, device_id=0):
        # ... initialization ...
        pass

    def get_image(self):
        # ... capture frame ...
        return image