Does anyone have an example of Template Sensors / Triggers?

[Tokyo]

This seems to work:

template:
    - sensor:
        - unique_id: lowest_battery_level
          name: "Lowest Battery Level"
          unit_of_measurement: "%"
          state: >-
            {% set x = (states.sensor | rejectattr('attributes.attribution', 'eq', 'Data provided by Apple iCloud') | rejectattr('state', 'in', ['unavailable']) | selectattr('attributes.device_class', 'eq', 'battery')  ) %}
            {% set lowest_battery = namespace(entity=0, value=1000) %}
            {% for y in x %}
                {% if (y.state | int) < lowest_battery.value %}
                {% set lowest_battery.value = y.state | int %}
                {% set lowest_battery.entity = y %}
                {% endif %}
            {% endfor %}
            {{ lowest_battery.entity.state }}
          icon: >-
            {% set battery_level = states.sensor.lowest_battery_level.state|default(0)|int %}
            {% set battery_round = (battery_level / 10) |int * 10 %}
            {% if battery_round >= 100 %}
              mdi:battery
            {% elif battery_round > 0 %}
              mdi:battery-{{ battery_round }}
            {% else %}
              mdi:battery-alert
            {% endif %}
          attributes:
            sensor_name: >-
              {% set x = (states.sensor | rejectattr('attributes.attribution', 'eq', 'Data provided by Apple iCloud') | rejectattr('state', 'in', ['unavailable']) | selectattr('attributes.device_class', 'eq', 'battery')  ) %}
              {% set lowest_battery = namespace(entity=0, value=1000) %}
              {% for y in x %}
                {% if (y.state | int) < lowest_battery.value %}
                {% set lowest_battery.value = y.state | int %}
                {% set lowest_battery.entity = y %}
                {% endif %}
              {% endfor %}
              {{ lowest_battery.entity.name }}

[Didgeridrew]

That almost worked for me… I had to add “unknown” to the rejectattr and to get rid of a few straggling battery_state sensors that would return “charging”, “discharging”, etc I switched the device_class-based selecattr for:

| selectattr('entity_id', 'search', 'battery_level')

{% set x = (states.sensor 
| rejectattr('attributes.attribution', 'eq', 'Data provided by Apple iCloud') 
| rejectattr('state', 'in', ['unavailable', 'unknown']) 
| selectattr('entity_id', 'search', 'battery_level') ) %}
{% set lowest_battery = namespace(entity=0, value=1000) %}
{% for y in x %}
    {% if (y.state | int) < lowest_battery.value %}
    {% set lowest_battery.value = y.state | int %}
    {% set lowest_battery.entity = y %}
    {% endif %}
{% endfor %}
{{ lowest_battery.entity.state }}

[Tokyo]

You seem to know this stuff very well. Are there any write ups or tutorials or is it a matter of trial and error?

@Didgeridrew

That almost worked for me… I had to add “unknown” to the rejectattr and to get rid of a few straggling battery_state sensors that would return “charging”, “discharging”, etc I switched the device_class-based selectattr to selectattr(‘entity_id’, ‘search’, ‘battery_level’).

I assume this searches for entities with entity id which includes battery_level. Is there a change that an entity is missed? Probably the same could be said for selecting entities which belongs to the device class battery. I found one entity which is of the device class battery and has entity id sensor.tradfri_remote_control.

By the way, just curious, what does the ‘-’ in state: > vs state: >- ?

[Didgeridrew]

Just like you, I’m no expert and I’m still learning… there are members on this forum who know this stuff way better than me. I just try to help out where I can.

I learned a lot of the basics from Youtube videos, from searching this forum, and from reading the Jinja template designer page, and the Home Assistant docs

Yes, there is a chance that an entity or two are missed with this template, or any other template. There are a lot of devices that work with Home Assistant, but not all integrations expose device information in the same format. If you have an entity that doesn’t create its own battery_level sensor, there are a couple methods that can be used to have that entity work with this template. I would just create a battery_level sensor using a template sensor.

The difference between “>” and “>-” can be found here. Either one will work for Home Assistant templates, I use “>-” out of habit more than necessity.

[Tokyo]

@Didgeridrew

I just try to help out where I can.

Very much appreciated. I learned a lot from going through this exercise.

I still prefer to filter on the device class because if the device class is battery, I can assume state is the battery level. After some polishing I can up with this.

template:
    - sensor:
        - unique_id: lowest_battery_level
          name: >-
            {# get list of battery entities #}
            {% set battery_entities = (states.sensor | rejectattr('attributes.attribution', 'eq', 'Data provided by Apple iCloud') | rejectattr('state', 'in', ['unavailable', 'unknown']) | selectattr('attributes.device_class', 'eq', 'battery')  ) %}
            {# get entity with lowest battery state #}
            {% set lowest_battery = namespace(entity=0, value=101) %}
            {% for x in battery_entities %}
                {% if (x.state | int) < lowest_battery.value %}
                    {% set lowest_battery.value = x.state | int %}
                    {% set lowest_battery.entity = x %}
                {% endif %}
            {% endfor %}
            {% if lowest_battery.entity %}
                {{ lowest_battery.entity.name }}
            {% else %}
                {{ "unknown" }}
            {% endif %}
          state: >-
            {# get list of battery entities #}
            {% set battery_entities = (states.sensor | rejectattr('attributes.attribution', 'eq', 'Data provided by Apple iCloud') | rejectattr('state', 'in', ['unavailable', 'unknown']) | selectattr('attributes.device_class', 'eq', 'battery')  ) %}
            {# get entity with lowest battery state #}
            {% set lowest_battery = namespace(entity=0, value=101) %}
            {% for x in battery_entities %}
                {% if (x.state | int) < lowest_battery.value %}
                    {% set lowest_battery.value = x.state | int %}
                    {% set lowest_battery.entity = x %}
                {% endif %}
            {% endfor %}
            {% if lowest_battery.entity %}
                {{ lowest_battery.entity.state }}
            {% else %}
                {{ "unknown" }}
            {% endif %}
          unit_of_measurement: "%"
          icon: >-
            {% set battery_level = states.sensor.lowest_battery_level.state|default(0)|int %}
            {% set battery_round = (battery_level / 10) |int * 10 %}
            {% if battery_round >= 100 %}
              mdi:battery
            {% elif battery_round > 0 %}
              mdi:battery-{{ battery_round }}
            {% else %}
              mdi:battery-alert
            {% endif %}

The only thing I am not have with is that I need to filter and iterate through the entities multiple times and wish there is a way to do that once and refer to the resulting entity multiple times.

[Didgeridrew]

There are a few feature request posts to have the ability to use variables added to Template Sensors… but until that happens you’re only other option is:

Template sensor: Declare variable in value_template to use in attribute_templates?

until the FR will be implemented, I believe the safest (probably also easiest) way is to write ‘base’ template sensors for your variable, and reference the state of that base sensor in the bigger template sensors, (in which state: field you can now also use the base sensor) Main and very important advantage of this construct is that the base sensor is called only once, and all template derived fields are updated based on that exact same value.

[Tokyo]

I have a follow up question regarding trigger based sensors. The documentation for trigger sensors states: trigger list (optional) Define an automation trigger to update the entities. Optional. If omitted will update based on referenced entities.
What would be the difference between

template:
  - sensor:

and

template:
  - trigger:
    sensor: