Set defaults for weather forecast sensor

Configuration
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1

I have several automations that use data from the weather_forecast sensor. The sensor is configured as below (including a forced update on HAss restart).

# Weather forecast - met.no
- sensor:
  - name: Daily weather forecast - met.no
    unique_id: weather_forecast_daily
    state: "{{ now().isoformat() }}"
    attributes:
      forecast: "{{ daily_forecast['weather.home'].forecast }}" 
  trigger:
  - platform: time_pattern
    hours: /1
  # Force sensor to be populated on restart
  - platform: homeassistant
    event: start
  # and on template entity reload - https://community.home-assistant.io/t/updating-a-trigger-based-template-on-startup/315677
  - platform: event
    event_type: event_template_reloaded
  action:
  - service: weather.get_forecasts
    data:
      type: daily
    target:
      entity_id: 
      - weather.home
      #- weather.home_2
    response_variable: daily_forecast

However, when HAss restarts, there seems to be a short interval in which the sensor values are not populated. Which means that all my automations/code that use the sensor crash.

The sensor data is accessed like this:

{{ state_attr('sensor.daily_weather_forecast', 'forecast')[0].condition }}

And, for example, the homeassistant-streamdeck-yaml code crashes on HAss restart, because for a brief moment there is no [0] in that list.

My questions are:

  1. Is there a way to avoid that brief moment in which the attribute is ‘None’?
  2. If not, what would be a proper way to set some sane defaults to be used during that brief interval?
2

I think there is an availability option for templates handling weather entities.

3

That is interesting - thank you!

However, state_attr still seems to return values for unavailable entities, so I assume it will still crash on that [0] index. My question is more on “how do I check if there is anything in the list?” :slight_smile:

4

Haven’t used either of these, but based on the docs the following events seem promising for your usecase:

  • Use the homeassistant_started event instead of the dedicated homeassistant_start trigger. This seems to imply that the event will only fire after the entire startup process is complete, rather than firing when it’s started.
  • Use the component_loaded event for your weather service. However note the below warning, so you might need to add a delay for that specific trigger.
Thus this event can not be used to run automations during startup as it would have missed these events
5

Look at the availability parameter in this template sensor.

    - name: "Precipitation Probability Today"
      unique_id: precipitation_probability_today
      icon: mdi:weather-rainy
      unit_of_measurement: "%"
      state: "{{ state_attr('sensor.daily_envcan', 'forecast')[0]['precipitation_probability'] | int(none) }}"
      attributes:
        provider: "Environment Canada" 
      availability: >
        {{ state_attr('sensor.daily_envcan', 'forecast') != none
            and state_attr('sensor.daily_envcan', 'forecast')[0] is defined
            and state_attr('sensor.daily_envcan', 'forecast')[0]['precipitation_probability'] is defined
            and is_number(state_attr('sensor.daily_envcan', 'forecast')[0]['precipitation_probability']) }}