Events
The core of Home Assistant is the event bus. The event bus allows any component to fire or listen for events. It is the core of everything. For example, any state change will be announced on the event bus as a state_changed event containing the previous and the new state of an entity.
Home Assistant contains a few built-in events that are used to coordinate between various components.
Event homeassistant_start
Event homeassistant_start is fired when all components from the configuration have been intitialized. This is the event that will start the timer firing off time_changed events.
Starting 0.42, it is no longer possible to listen for event homeassistant_start. Use the ‘homeassistant’ platform instead.
Event homeassistant_stop
Event homeassistant_stop is fired when Home Assistant is shutting down. It should be used to close any open connection or release any resources.
Event state_changed
Event state_changed is fired when a state changes. Both old_state and new_state are state objects. Documentation about state objects.
| Field | Description |
|---|---|
entity_id |
Entity ID of the changed entity. Example: light.kitchen |
old_state |
The previous state of the entity before it changed. This field is omitted if the entity is new. |
new_state |
The new state of the entity. This field is omitted if the entity is removed from the state machine. |
Event time_changed
Event time_changed is fired every second by the timer and contains the current time.
| Field | Description |
|---|---|
now |
A datetime object containing the current time in UTC. |
Event service_registered
Event service_registered is fired when a new service has been registered within Home Assistant.
| Field | Description |
|---|---|
domain |
Domain of the service. Example: light. |
service |
The service to call. Example: turn_on |
Event call_service
Event call_service is fired to call a service.
| Field | Description |
|---|---|
domain |
Domain of the service. Example: light. |
service |
The service to call. Example: turn_on |
service_data |
Dictionary with the service call parameters. Example: { 'brightness': 120 }. |
service_call_id |
String with a unique call id. Example: 23123-4. |
Event service_executed
Event service_executed is fired by the service handler to indicate the service is done.
| Field | Description |
|---|---|
service_call_id |
String with the unique call id of the service call that was executed. Example: 23123-4. |
Event platform_discovered
Event platform_discovered is fired when a new platform has been discovered by the discovery component.
| Field | Description |
|---|---|
service |
The platform that is discovered. Example: zwave. |
discovered |
Dictionary containing discovery information. Example: { "host": "192.168.1.10", "port": 8889}. |
Event component_loaded
Event component_loaded is fired when a new component has been loaded and initialized.
| Field | Description |
|---|---|
component |
Domain of the component that has just been initialized. Example: light. |