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Entities are the building blocks of Home Assistant. They represent devices, sensors, switches, and other controllable or monitorable objects. This guide covers how to create entity components for your integration.

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Entity Basics

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What is an Entity?

An entity represents a single piece of functionality from a device or service. Examples:
  • A temperature sensor
  • A light bulb
  • A media player
  • A switch
Each entity has:
  • A unique ID for identification
  • A state (on/off, temperature value, etc.)
  • attributes with additional information
  • An entity ID like sensor.living_room_temperature

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Entity Platforms

Home Assistant has different entity platforms for different types of entities:
  • sensor - Read-only measurements
  • binary_sensor - On/off sensors
  • switch - On/off switches
  • light - Lights with brightness, color, etc.
  • climate - Thermostats and climate control
  • cover - Blinds, garage doors, etc.
  • And many more…

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Creating an Entity Platform

Each entity platform is a separate Python file in your integration directory.

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Platform Setup Function

Every platform must have an async_setup_entry function:
sensor.py
"""Sensor platform for Your Integration."""
from __future__ import annotations

from homeassistant.components.sensor import (
    SensorDeviceClass,
    SensorEntity,
    SensorStateClass,
)
from homeassistant.config_entries import ConfigEntry
from homeassistant.const import UnitOfTemperature
from homeassistant.core import HomeAssistant
from homeassistant.helpers.entity_platform import AddEntitiesCallback

from .const import DOMAIN


async def async_setup_entry(
    hass: HomeAssistant,
    entry: ConfigEntry,
    async_add_entities: AddEntitiesCallback,
) -> None:
    """Set up the sensor platform."""
    # Get the API client or coordinator from hass.data
    client = hass.data[DOMAIN][entry.entry_id]["client"]
    
    # Fetch the list of sensors
    sensors = await client.get_sensors()
    
    # Create entity objects
    entities = [
        YourTemperatureSensor(client, sensor_id)
        for sensor_id in sensors
    ]
    
    # Add entities to Home Assistant
    async_add_entities(entities)

​
Creating an Entity Class

Entity classes inherit from a base entity class specific to their platform.

​
Basic Entity Example

class YourTemperatureSensor(SensorEntity):
    """Representation of a temperature sensor."""
    
    # Specify the device class
    _attr_device_class = SensorDeviceClass.TEMPERATURE
    # Specify the state class for statistics
    _attr_state_class = SensorStateClass.MEASUREMENT
    # Specify the unit
    _attr_native_unit_of_measurement = UnitOfTemperature.CELSIUS
    
    def __init__(self, client, sensor_id: str) -> None:
        """Initialize the sensor."""
        self._client = client
        self._sensor_id = sensor_id
        
        # Set a unique ID - important for customization
        self._attr_unique_id = f"{DOMAIN}_{sensor_id}"
        # Set the entity name
        self._attr_name = f"Temperature {sensor_id}"
    
    async def async_update(self) -> None:
        """Fetch new state data for the sensor."""
        # Get the current temperature from the API
        temperature = await self._client.get_temperature(self._sensor_id)
        self._attr_native_value = temperature

​
Entity Properties

The Entity base class provides many properties you can override:

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Essential Properties

class YourEntity(SensorEntity):
    """Your entity."""
    
    # Unique identifier for this entity
    _attr_unique_id = "unique_entity_id"
    
    # Display name
    _attr_name = "My Sensor"
    
    # Whether the entity is available
    _attr_available = True
    
    # Icon to display (from Material Design Icons)
    _attr_icon = "mdi:thermometer"

​
Modern Entity Naming

Use the modern naming pattern with device info: 
from homeassistant.helpers.device_registry import DeviceInfo

class YourSensor(SensorEntity):
    """Representation of a sensor."""
    
    # This entity represents a device
    _attr_has_entity_name = True
    # The entity name (will be combined with device name)
    _attr_name = "Temperature"
    
    def __init__(self, device_id: str) -> None:
        """Initialize the sensor."""
        self._attr_unique_id = f"{device_id}_temperature"
        
        # Associate this entity with a device
        self._attr_device_info = DeviceInfo(
            identifiers={(DOMAIN, device_id)},
            name="My Device",
            manufacturer="Your Company",
            model="Model X",
            sw_version="1.0.0",
        )
This creates an entity named “My Device Temperature” and groups it with other entities from the same device.

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State Updates

There are several ways to update entity state:

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Method 1: async_update (Polling)

class YourSensor(SensorEntity):
    """Polling sensor."""
    
    # Enable polling (default is True)
    _attr_should_poll = True
    
    async def async_update(self) -> None:
        """Fetch new state data for the sensor."""
        # This will be called periodically by Home Assistant
        self._attr_native_value = await self._client.get_value()

class YourSensor(SensorEntity):
    """Push-based sensor."""
    
    # Disable polling since we'll push updates
    _attr_should_poll = False
    
    def __init__(self, client) -> None:
        """Initialize the sensor."""
        self._client = client
        # Register a callback for updates
        self._client.register_callback(self._handle_update)
    
    def _handle_update(self, value) -> None:
        """Handle a pushed update from the API."""
        self._attr_native_value = value
        # Tell Home Assistant the state changed
        self.async_write_ha_state()
    
    async def async_will_remove_from_hass(self) -> None:
        """Clean up when entity is removed."""
        # Unregister the callback
        self._client.unregister_callback(self._handle_update)

​
Method 3: DataUpdateCoordinator (Best Practice)

from homeassistant.helpers.update_coordinator import (
    CoordinatorEntity,
    DataUpdateCoordinator,
)

class YourSensor(CoordinatorEntity, SensorEntity):
    """Sensor using coordinator."""
    
    def __init__(
        self,
        coordinator: DataUpdateCoordinator,
        sensor_id: str,
    ) -> None:
        """Initialize the sensor."""
        super().__init__(coordinator)
        self._sensor_id = sensor_id
        self._attr_unique_id = f"{DOMAIN}_{sensor_id}"
    
    @property
    def native_value(self):
        """Return the state of the sensor."""
        # Access coordinated data
        return self.coordinator.data[self._sensor_id]
See the DataUpdateCoordinator documentation for setup details.

​
Platform-Specific Features

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Sensor Platform

from homeassistant.components.sensor import (
    SensorDeviceClass,
    SensorEntity,
    SensorStateClass,
)

class YourSensor(SensorEntity):
    """A sensor entity."""
    
    # Device class affects how the entity is displayed
    _attr_device_class = SensorDeviceClass.TEMPERATURE
    
    # State class enables statistics and long-term data
    _attr_state_class = SensorStateClass.MEASUREMENT
    
    # Native value and unit
    _attr_native_value = 20.5
    _attr_native_unit_of_measurement = UnitOfTemperature.CELSIUS
    
    # Precision for rounding
    _attr_suggested_display_precision = 1

​
Switch Platform

from homeassistant.components.switch import SwitchEntity

class YourSwitch(SwitchEntity):
    """A switch entity."""
    
    @property
    def is_on(self) -> bool:
        """Return true if switch is on."""
        return self._attr_is_on
    
    async def async_turn_on(self, **kwargs) -> None:
        """Turn the switch on."""
        await self._client.turn_on(self._device_id)
        self._attr_is_on = True
        self.async_write_ha_state()
    
    async def async_turn_off(self, **kwargs) -> None:
        """Turn the switch off."""
        await self._client.turn_off(self._device_id)
        self._attr_is_on = False
        self.async_write_ha_state()

​
Light Platform

from homeassistant.components.light import (
    ATTR_BRIGHTNESS,
    ColorMode,
    LightEntity,
)

class YourLight(LightEntity):
    """A light entity."""
    
    # Supported color modes
    _attr_supported_color_modes = {ColorMode.BRIGHTNESS}
    _attr_color_mode = ColorMode.BRIGHTNESS
    
    @property
    def brightness(self) -> int | None:
        """Return the brightness of this light between 0..255."""
        return self._attr_brightness
    
    @property
    def is_on(self) -> bool:
        """Return true if light is on."""
        return self._attr_is_on
    
    async def async_turn_on(self, **kwargs) -> None:
        """Turn the light on."""
        if ATTR_BRIGHTNESS in kwargs:
            brightness = kwargs[ATTR_BRIGHTNESS]
            await self._client.set_brightness(self._device_id, brightness)
            self._attr_brightness = brightness
        
        await self._client.turn_on(self._device_id)
        self._attr_is_on = True
        self.async_write_ha_state()
    
    async def async_turn_off(self, **kwargs) -> None:
        """Turn the light off."""
        await self._client.turn_off(self._device_id)
        self._attr_is_on = False
        self.async_write_ha_state()

​
Entity Attributes

You can add extra attributes to entities: 
class YourSensor(SensorEntity):
    """Sensor with extra attributes."""
    
    @property
    def extra_state_attributes(self) -> dict[str, Any]:
        """Return extra state attributes."""
        return {
            "last_update": self._last_update,
            "battery_level": self._battery_level,
            "signal_strength": self._signal_strength,
        }

​
Entity Categories

Use entity categories to organize entities: 
from homeassistant.const import EntityCategory

class YourDiagnosticSensor(SensorEntity):
    """A diagnostic sensor."""
    
    # This entity is diagnostic (shown in advanced section)
    _attr_entity_category = EntityCategory.DIAGNOSTIC

class YourConfigSwitch(SwitchEntity):
    """A configuration switch."""
    
    # This entity is for configuration
    _attr_entity_category = EntityCategory.CONFIG
Categories:
  • EntityCategory.CONFIG - Configuration entities
  • EntityCategory.DIAGNOSTIC - Diagnostic information
  • None - Primary entities (default)

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Entity Registry

When you set a unique_id, entities are automatically registered: 
class YourEntity(SensorEntity):
    """Entity with unique ID."""
    
    def __init__(self, device_id: str) -> None:
        """Initialize."""
        # This enables entity registry features:
        # - User can customize the entity
        # - Entity survives integration reload
        # - Entity can be disabled
        self._attr_unique_id = f"{DOMAIN}_{device_id}"
Benefits of entity registry:
  • Users can customize entity names and icons
  • Users can disable entities they don’t need
  • Entity IDs are stable across restarts
  • Entities can be tracked across config changes

​
Dynamic Entity Addition

For devices that support dynamic entities: 
from homeassistant.helpers.entity_platform import AddEntitiesCallback

async def async_setup_entry(
    hass: HomeAssistant,
    entry: ConfigEntry,
    async_add_entities: AddEntitiesCallback,
) -> None:
    """Set up the platform."""
    client = hass.data[DOMAIN][entry.entry_id]["client"]
    
    # Add initial entities
    async_add_entities([YourSensor(client, "sensor1")])
    
    # Store the callback for later use
    hass.data[DOMAIN][entry.entry_id]["add_entities"] = async_add_entities

# Later, when a new device is discovered:
def handle_new_device(hass, entry_id, device_id):
    """Handle a newly discovered device."""
    add_entities = hass.data[DOMAIN][entry_id]["add_entities"]
    client = hass.data[DOMAIN][entry_id]["client"]
    
    # Add the new entity
    add_entities([YourSensor(client, device_id)])

​
Entity Availability

Indicate when an entity is unavailable: 
class YourSensor(SensorEntity):
    """Sensor that may become unavailable."""
    
    async def async_update(self) -> None:
        """Update the sensor."""
        try:
            self._attr_native_value = await self._client.get_value()
            self._attr_available = True
        except ConnectionError:
            # Device is offline
            self._attr_available = False

​
Best Practices

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Always Use Unique IDs

Provide unique IDs for all entities to enable customization: 
self._attr_unique_id = f"{entry.entry_id}_{device_id}_{sensor_type}"

​
Use Device Info

Group related entities under a single device: 
self._attr_device_info = DeviceInfo(
    identifiers={(DOMAIN, device_id)},
    name="Device Name",
    manufacturer="Manufacturer",
    model="Model",
)

​
Use DataUpdateCoordinator

For polling integrations, use DataUpdateCoordinator to efficiently manage updates.

​
Disable Polling When Possible

If your API supports push updates, disable polling: 
_attr_should_poll = False

​
Handle Exceptions

Gracefully handle API errors: 
try:
    value = await self._client.get_value()
except APIError:
    _LOGGER.error("Failed to update sensor")
    self._attr_available = False

​
Use Modern Naming

Set _attr_has_entity_name = True and provide device info for better entity naming.

​
Common Patterns

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Entity Descriptions

For multiple similar entities, use entity descriptions: 
from dataclasses import dataclass
from homeassistant.components.sensor import SensorEntityDescription

@dataclass
class YourSensorDescription(SensorEntityDescription):
    """Describes a sensor."""
    api_key: str | None = None

SENSOR_TYPES: tuple[YourSensorDescription, ...] = (
    YourSensorDescription(
        key="temperature",
        name="Temperature",
        device_class=SensorDeviceClass.TEMPERATURE,
        api_key="temp",
    ),
    YourSensorDescription(
        key="humidity",
        name="Humidity",
        device_class=SensorDeviceClass.HUMIDITY,
        api_key="humid",
    ),
)

class YourSensor(SensorEntity):
    """Sensor using description."""
    
    def __init__(self, description: YourSensorDescription) -> None:
        """Initialize."""
        self.entity_description = description
        self._attr_unique_id = f"{DOMAIN}_{description.key}"

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