Simple Matter on/off handler in Python. See https://stackoverflow.com/a/74992066/3041544

lighting.py

from chip.server import (
    GetLibraryHandle,
    PostAttributeChangeCallback,
)

CLUSTER_ONOFF = 6
ATTR_ONOFF = 0


@PostAttributeChangeCallback
def attributeChangeCallback(endpoint: int, clusterId: int, attributeId: int, xx_type: int, size: int, value: bytes):
    if endpoint == 1:
        if clusterId == CLUSTER_ONOFF and attributeId == ATTR_ONOFF:
            if value and value[0] == 1:
                print(">>> on <<<")
            else:
                print(">>> off <<<")


chipLib = GetLibraryHandle(attributeChangeCallback)

input('Press any key to exit')