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The homeassistant module is the main entry point for Home Assistant Core. It provides the foundational components for the home automation framework.

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Overview

Home Assistant is a home automation framework for observing the state of entities and reacting to changes. The core module provides:
  • Event System: Fire and listen to events throughout the system
  • State Machine: Track and manage entity states
  • Service Registry: Register and call services
  • Config Entries: Manage integration configurations
  • Integration Loader: Load and manage integrations

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Core Components

The main components accessible through the homeassistant module:

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HomeAssistant Instance

The HomeAssistant class is the root object that coordinates all home automation functionality. See Core APIs for details.

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Event Bus

The event bus (EventBus) allows components to fire and listen for events. Events are the primary way components communicate with each other.

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State Machine

The state machine (StateMachine) tracks the state of all entities in the system. It provides methods to get, set, and remove entity states.

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Service Registry

The service registry (ServiceRegistry) manages all available services that can be called by users or automations.

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Key Concepts

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Entities

Entities are the fundamental building blocks in Home Assistant. Each entity has:
  • A unique entity ID (format: domain.object_id)
  • A state (string value)
  • Attributes (dictionary of additional data)
  • A context (tracking who/what triggered changes)

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Events

Events are fired when something happens in Home Assistant. Common events include:
  • state_changed: When an entity’s state changes
  • service_registered: When a new service is registered
  • homeassistant_start: When Home Assistant starts
  • homeassistant_stop: When Home Assistant stops

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Services

Services are callable actions that perform specific tasks. They are organized by domain and can accept parameters.

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Module Structure

homeassistant/
├── __init__.py          # Main module
├── core.py              # Core classes (HomeAssistant, State, Event, etc.)
├── config_entries.py    # Configuration entry management
├── loader.py            # Integration loading system
└── components/          # Built-in integrations

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Usage Example

from homeassistant.core import HomeAssistant, callback

# Get the HomeAssistant instance (in async context)
async def my_setup(hass: HomeAssistant):
    # Access the state machine
    state = hass.states.get("light.living_room")
    
    # Set a state
    hass.states.async_set(
        "sensor.my_sensor",
        "23.5",
        {"unit_of_measurement": "°C"}
    )
    
    # Listen for events
    @callback
    def handle_event(event):
        print(f"Event fired: {event.event_type}")
    
    hass.bus.async_listen("my_event", handle_event)
    
    # Call a service
    await hass.services.async_call(
        "light",
        "turn_on",
        {"entity_id": "light.living_room"}
    )

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Version

The current version is available via: 
from homeassistant.const import __version__
print(__version__)

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