Possible error in binary sensor attributes?

This is driving me nuts! In the template editor, I tested the two statements below that aim at obtaining the last state change of a network ping:

1 (correct result):

{{ as_timestamp(states.binary_sensor.net_network_bsm.last_changed) }}

2 (error):

{{ as_timestamp(states(‘binary_sensor.net_network_bsm’).last_changed) }}

The first one returns a correct time, but the second returns the error:

ValueError: Template error: as_timestamp got invalid input ‘’ when rendering template ‘{{ as_timestamp(states.binary_sensor.net_network_bsm.last_changed) }} {{ as_timestamp(states(‘binary_sensor.net_network_bsm’).last_changed) }}’ but no default was specified

ChatGPT confirms (and I totally agree) that the second statement is the correct way to obtain this timestamp, but no cigar…

What is wrong here?

You’re both wrong.

The states() function returns a string, not a state object.
Generically, the proper way to get an attribute value is by using state_attr("<entity_id>", "<attribute_name>"), but last_modified / last_changed cannot be obtained that way, so your 1st form is the only correct way for those.


Thanks for your help! I’d already found out that the last_changed attribute wasn’t present for this entity, so after searching I stumbled upon the first, working method.

My next question is: WHY can’t this attribute not be accessed in the proper way, using state_attr, since its value is obviously present.

The function I am trying to build is one that checks the last state change of several network devices, so I need to feed it a variable entity_id. But, for the same reasons you gave in your reply, this also won’t work (tried it):

{% set entity = ‘states.binary_sensor.net_network_bsm.last_changed’ %}
{{ as_timestamp(entity) }}

How do I solve this? I see no plausible path for a solution.

I think because those are not actual attributes, but properties of the state object.

You’re confused between string and objects.

This works (remove the quotes)

{% set entity = states.binary_sensor.net_network_bsm.last_changed %}
{{ as_timestamp(entity) }}

You’ll have to pass a list of state objects to you function, rather than a string list of entity id.

Thanks for your very useful help; I see now where things go wrong…
It works indeed, but I guess the only way to make the entity “variable”, i.e. feeding the timestamp function various state objects such as:


is by using a selector or a macro; or is there a trick that allows me to change part of the state objects name?

Even if it did exist the template would still fail because it’s fundamentally wrong. I see that ChatGPT continues to be a poor reference for Home Assistant, confidently suggesting nonsense.

The states() function returns the value of an entity’s state property and it’s always a string. ChatGPT led you to believe that a string value can have a property like last_changed but it doesn’t.

If the entity’s last_changed property is defined and has a value, either of these will work:

{{ as_timestamp(states.binary_sensor.net_network_bsm.last_changed) }}
{{ as_timestamp(states['binary_sensor.net_network_bsm'].last_changed) }}


I suggest you review the documentation for State Objects. You’ll see that attributes and last_changed are properties of a State Object. The state_attr() function is designed to work with a State Object’s attributes property (and nothing else).

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{% set x = 'binary_sensor.foo' %}
{{ as_timestamp(states[x].last_changed) }}

Set the variable’s value using whatever means that is appropriate for your intended application.


Great! That works and solves my problem!
While you were thinking up this solution, I’ve challenged ChatGPT to find one too; it came up with a gazillion of other solutions, none of them worked…
So a human is still better than AI…

Great job and thanks again

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It’s why this policy was instituted:

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I didn’t know about this policy; good to know and a very sensible one!

So far, I’ve used ChatGPT to give myself a “head start” in writing code (again); I am a former programmer from the assembler / C++ era. ChatGPT was certainly helpful and already saved me many hours browsing and googling, but I’ve also learned that on many occasions it is totally lost. But as with all information obtained from the Internet, one should always have a critical mind towards it.