Test if none: none

The none test checks whether a value is None. It returns true if the value is None and false otherwise.

In Home Assistant, None can appear in various situations: an attribute that does not exist on an entityAn entity represents a sensor, actor, or function in Home Assistant. Entities are used to monitor physical properties or to control other entities. An entity is usually part of a device or a service. [Learn more], a function that returns nothing, or a variable that has been explicitly set to None. Testing for None is different from testing for undefined: a variable can be defined but have a value of None. This test helps you distinguish between “not set” and “set to nothing.”

Usage

Here’s how to use this template function. Copy any example and adjust it to your setup.

{% if value is none %}
  Value is None
{% endif %}

Value is None

Function signature

The signature is a technical summary of this template function. It shows the name of the function, the values (called parameters) it accepts, and what type of data each parameter expects (for example, a piece of text or a number).

Function parameters that have a = with a value after them are optional. If you leave them out, the default value shown is used automatically. Function parameters without a default are required.

none(
    value: Any,
) -> bool

Function parameters

The following parameters can be provided to this test.

Good to know

• This is different from undefined. A variable can be defined and still be None.
• The string "None" does not pass this test, only the actual None value does.

Try it yourself

Ready to test this? Open Developer tools > Template, paste the example into the Template editor, and watch the result update on the right. Edit the values to see how the function adapts to your own entitiesAn entity represents a sensor, actor, or function in Home Assistant. Entities are used to monitor physical properties or to control other entities. An entity is usually part of a device or a service. [Learn more].

More examples

Real scenarios where this function comes up in automations and templates. Copy any example and adapt it to your setup.

Check for missing attributes

Test whether an entityAn entity represents a sensor, actor, or function in Home Assistant. Entities are used to monitor physical properties or to control other entities. An entity is usually part of a device or a service. [Learn more] attribute exists before using it.

{% if state_attr("climate.thermostat", "preset_mode") is none %}
  No preset mode available
{% else %}
  Preset: {{ state_attr("climate.thermostat", "preset_mode") }}
{% endif %}

No preset mode available

Guard against None in calculations

Ensure a value is not None before performing math.

{% set temp = state_attr("weather.home", "temperature") %}
{% if temp is none %}
  Temperature unavailable
{% else %}
  {{ temp | round(1) }} degrees
{% endif %}

21.5 degrees

Still stuck?

The Home Assistant community is quick to help: join Discord for real-time chat, post on the community forum with your template and expected result, or share on our subreddit /r/homeassistant.

Related template functions

These functions work well alongside this one:

• Test if defined: defined - Tests whether a variable is defined (not undefined).

• Test if undefined: undefined - Tests whether a variable is undefined.

• Set a default value: default - Provides a default value if a variable is undefined or none.

• Check if entity has a value: has_value - Tests if an entity exists and has a valid state (not unavailable or unknown).