How to Do on / OFF group switch

Configuration
5

You can do a group toggle using a Python script that you call from an automation for example:

state = hass.states.get(data['master']).state

if state == 'on':
    hass.services.call('homeassistant', 'turn_off',
                       {'entity_id': data['slave']})
else:
    hass.services.call('homeassistant', 'turn_on', {
                       'entity_id': data['slave']})

In automations.yaml:

- alias: "Toggle a group"
  trigger:
 ...
  action:
    service: python_script.master_toggle
    data:
      master: light.living_room_master_light
      slave: group.living_room_lights