Sum values in array

[PhillyGilly1 (Philly Gilly)]

I want to know the Solar Forecast between midnight and midday adding up the hourly values from the Solcast Forecast which are in the entity sensor.solcast_pv_forecast_forecast_today state attributes e.g.

detailedHourly:
  - period_start: '2023-10-26T00:00:00+01:00'
    pv_estimate: 0
    pv_estimate10: 0
    pv_estimate90: 0
  - period_start: '2023-10-26T01:00:00+01:00'
    pv_estimate: 0
    pv_estimate10: 0
    pv_estimate90: 0

I can pick out individual values for example the 12th hour thus:

{{ "%.3f"|format(state_attr('sensor.solcast_pv_forecast_forecast_today','detailedHourly')[12]['pv_estimate']|float)}}

However when I try to sum these up in a for loop, the values don’t add. My initial attempt using “+=” convention was completely rejected in the template editor

{%- set forecast_to_12_today = 0|float %}
{%- for values in [0,1,2,3,4,5,6,7,8,9,10,11] %}
{%- set forecast_to_12_today += "%.3f"|format(state_attr('sensor.solcast_pv_forecast_forecast_today','detailedHourly')[values|int]['pv_estimate'])|float %}
{{ forecast_to_12_today}}
{%- endfor %}

and even when I went to brute force the value resets each loop instead of incrementing.

{%- set forecast_to_12_today = 0|float %}
{%- for values in [0,1,2,3,4,5,6,7,8,9,10,11] %}
{%- set forecast_to_12_today = forecast_to_12_today + "%.3f"|format(state_attr('sensor.solcast_pv_forecast_forecast_today','detailedHourly')[values|int]['pv_estimate'])|float %}
{{ forecast_to_12_today}}
{%- endfor %}

Any help appreciated. TIA.

[123 (Taras)]

Copy-paste the following template into the Template Editor and confirm it reports the correct value:

{{ state_attr('sensor.solcast_pv_forecast_forecast_today', 'detailedHourly')
  | map(attribute='pv_estimate') | sum | round(3) }}

The template assumes pv_estimate contains an int or float value. If it’s actually a numeric string then the template will need an additional filter (to convert the strings to float).

---

NOTE

Regarding your for-loop example, changes to a variable inside a for-loop are not preserved outside of the for-loop unless the variable employs namespace.

How to simplify this binary_sensor template, using filters with count or loops?

A Jinja2 variable defined outside of a for loop can be assigned a different value inside the for loop but that value only exists inside the for loop. Outside of the for loop, the variable’s value remains unchanged by whatever may have been done inside the for loop. Obviously this presents a problem when you want the for loop to modify the variable’s value. That’s where namespace is useful. It allows you to define a Jinja2 variable that can be assigned a value inside a for loop that is retained …

[PhillyGilly1 (Philly Gilly)]

Thanks. The Template Editor reported OK. Your tip about namespace worked. Here is the final code:

{% set forecast_to_12_today = namespace(y=0) %}
{% for values in [6,7,8,9,10,11] %}
{%- set forecast_to_12_today.y = forecast_to_12_today.y + "%.3f"|format(state_attr('sensor.solcast_pv_forecast_forecast_today','detailedHourly')[values|int]['pv_estimate'])|float %}
{%- endfor %}
{{ forecast_to_12_today.y}}

[123 (Taras)]

@PhillyGilly1

The Template Editor reported OK. Your tip about namespace worked

Glad to hear it reported the correct value.

@PhillyGilly1

Here is the final code:

That’s still an unnecessarily long way to compute the sum of the last 6 items in the list. Here’s what I had suggested previously but constrained to sum only the last six pv_estimate values.

{{ state_attr('sensor.solcast_pv_forecast_forecast_today', 'detailedHourly')[6:]
  | map(attribute='pv_estimate') | sum | round(3) }}

[PhillyGilly1 (Philly Gilly)]

Thanks again. I get it now.
I actually want to sum up the values of solar PV generation in the morning.
There are 24 hourly values in the forecast: 0 through to 23. with 0 being the forecast from 00:00 to 01:00 and the values from 00:00 to 05:00 generally being zero. So in my long-hand version I just added values 6 to 11.
Using your approach I don’t need to worry about values 0 to 5 so this gets the same answer.

{{ state_attr('sensor.solcast_pv_forecast_forecast_tomorrow', 'detailedHourly')[:12]
| map(attribute='pv_estimate') | sum | round(3) }}

[123 (Taras)]

Glad to hear my suggested template solved the problem.

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