How to count entities in dynamic group?

[mystic violet]

I created a dynamic group to list devices with low battery level on dashboard. Works mostly:

alias: Dynamic Battery Group
description: Creates Group of Items with Low Battery Level on HA Startup
triggers:
  - trigger: homeassistant
    event: start
conditions: []
actions:
  - action: group.set
    metadata: {}
    data:
      object_id: low_battery
      name: Low Battery
      icon: mdi:battery-outline
      entities: >-
        {{ states.sensor | selectattr('attributes.device_class', 'defined') |
        selectattr('attributes.device_class', 'eq', 'battery') |
        rejectattr('entity_id', 'eq', 'SM-S906U') | selectattr('state',
        'lt','50') | map(attribute='entity_id') | list  }}
mode: single
```yaml

Questions:
1. The rejectattr line is not working to prevent my phone with HA companion app from being on the list.  Do I need to refer to that entity differently?
2. I have tried to create a separate template sensor to count the number of items in this dynamic group with no luck.  This is to be used as a badge on a dashboard.  Any example code on how to create this count sensor?

Any thoughts would be appreciated.

[limpid sky]

1. You are using entity_id in your rejectattr() filter, but SM-S906U is not an entity_id. An entity_id would be something like senor.sm_s906u_battery_level
2. The group will have an entity_id attribute, which will list all entities in the group, you can count the entities in that attriubte: {{ state_attr('group.your_group', 'entity_id') | count }}

BUT: your template for the entities will not do what you want it to do. You are doing a state comparison with strings

and string comparisons will give unwanted result, as they are compared character by character

so for example "6" < "50" will return false as 6 is higher than 5

[mystic violet]

Thanks. Very helpful. I'm good except your last point about string comparisons. I can use map('int', -1) and then do the number comparison but then I can't get the entity_ids back with the | list. I want the list of entity_ids with low batteries to be available on the dashboard too. I've got a conceptual error I guess. Any additional thoughts?

[dusky radish]

you can either:
create a for loop and iterate through each item so that you can cast the state to an int, check if it is <50, and if it is then you would append it to a namespace variable that is a list

-or-

make two lists (one with entity id's and one with states cast to int) and zip them together and then filter them.

this is the 2nd option, place it in developer tools -> template and see if it outputs what you expect

{% set sensors = states.sensor | selectattr('attributes.device_class', 'defined') | selectattr('attributes.device_class', 'eq', 'battery') | rejectattr('entity_id', 'eq', 'sensor.sm_s906u_battery_level') | list %}
{% set sensor_dict = zip(sensors | map(attribute='entity_id'), sensors | map(attribute='state') | map('int',-1)) %}
{{ sensor_dict | selectattr(1, 'lt', 50) | map(attribute=0) | list }}

[limpid sky]

I would add | selectattr('entity_id', 'has_value') to the first line to filter out non numeric states, then you also don't need the default in the int filter

like itis above, you will also get the sensors which are unavailable or unkown

{% set sensors = states.sensor
                  | selectattr('entity_id', 'has_value')
                  | selectattr('attributes.device_class', 'defined')
                  | selectattr('attributes.device_class', 'eq', 'battery')
                  | rejectattr('entity_id', 'eq', 'sensor.sm_s906u_battery_level')
                  | list
%}
{% set sensor_dict = zip(sensors | map(attribute='entity_id'), sensors | map(attribute='state') | map('int')) %}
{{ sensor_dict | selectattr(1, 'lt', 50) | map(attribute=0) | list }}