Home Assistant provides ready-made services for a lot of things, but it doesn't always cover everything. Instead of trying to change Home Assistant, it is preferred to add it as a service under your own integration first. Once we see a pattern in these services, we can talk about generalizing them.
This is a simple "hello world" example to show the basics of registering a service. To use this example, create the file
<config dir>/custom_components/hello_service/__init__.py and copy the below example code.
Services can be called from automations and from the service "Developer tools" in the frontend.
DOMAIN = "hello_service"
ATTR_NAME = "name"
DEFAULT_NAME = "World"
def setup(hass, config):
"""Set up is called when Home Assistant is loading our component."""
"""Handle the service call."""
name = call.data.get(ATTR_NAME, DEFAULT_NAME)
hass.services.register(DOMAIN, "hello", handle_hello)
# Return boolean to indicate that initialization was successful.
To load the integration in Home Assistant is necessary to create a
manifest.json and to add an entry in your
configuration.yaml. When your component is loaded, a new service should be available to call.
# configuration.yaml entry
An example of
"name": "Hello Service",
Open the frontend and in the sidebar, click the first icon in the developer tool section. This will open the Call Service developer tool. On the right, find your service and click on it. This will automatically fill in the correct values.
Pressing "Call Service" will now call your service without any parameters. This will cause your service to create a state with the default name 'World'. If you want to specify the name, you have to specify a parameter by providing it through Service Data. In YAML mode, add the following and press "Call Service again".
The service will now overwrite the previous state with "Planet".
Adding services is only useful if users know about them. In Home Assistant we use a
services.yaml as part of your integration to describe the services.
Services are published under the domain name of your integration, so in
services.yaml we only use the service name as the base key.
# Example services.yaml entry
# Service ID
# Service name as shown in UI
name: Set speed
# Description of the service
description: Sets fan speed.
# If the service accepts entity IDs, target allows the user to specify entities by
# entity, device, or area. If `target` is specified, `entity_id` should not be
# defined in the `fields` map. By default it shows only targets matching entities
# from the same domain as the service, but if further customization is required,
# target supports the entity, device, and area selectors
# (https://www.home-assistant.io/docs/blueprint/selectors/). Entity selector
# parameters will automatically be applied to device and area, and device selector
# parameters will automatically be applied to area.
# If not all entities from the service's domain support a service, entities
# can be further filtered by the `supported_features` state attribute. An
# entity will only be possible to select if it supports at least one of the
# listed supported features.
# Different fields that your service accepts
# Key of the field
# Field name as shown in UI
# Description of the field
description: Speed setting
# Whether or not field is required (default = false)
# Advanced fields are only shown when the advanced mode is enabled for the user
# (default = false)
# Example value that can be passed for this field
# The default field value
# Selector (https://www.home-assistant.io/docs/blueprint/selectors/) to control
# the input UI for this field
Filtering service fields
In some cases, entities from a service's domain may not support all service fields. By
filter for the field description, the field will only be shown if at least
one selected entity supports the field according to the configured filter.
A filter must specify either
attribute, combing both is not
supported_features filter is specified by of a list of supported features. The field
will be shown if at least one selected entity supports at least one of the listed features.
attribute filter combines an attribute with a list of values. The field will be
shown if at least one selected entity's attribute is set to one of the listed attribute states.
If the attribute state is a list, the field will be shown if at least one item in a selected
entity's attribute state is set to one of the listed attribute states.
This is a partial example of a field which is only shown if at least one selected entity
description: New target temperature for HVAC.
This is a partial example of a field which is only shown if at least one selected entity's
supported_color_modes attribute includes either
name: Color temperature
description: Color temperature for the light in mireds.
Sometimes you want to provide extra services to control your entities. For example, the Sonos integration provides services to group and ungroup devices. Entity services are special because there are many different ways a user can specify entities. It can use areas, a group or a list of entities.
You need to register entity services in your platforms, like
<your-domain>/media_player.py. These services will be made available under your domain and not the media player domain. Example code:
from homeassistant.helpers import config_validation as cv, entity_platform, service
async def async_setup_entry(hass, entry):
"""Set up the media player platform for Sonos."""
platform = entity_platform.async_get_current_platform()
# This will call Entity.set_sleep_timer(sleep_time=VALUE)
If you need more control over the service call, you can also pass an async function that instead of
async def custom_set_sleep_timer(entity, service_call):