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Transform list items: map

The map filter applies a transformation to each item in a list and returns the results. It can be used in two primary ways: extracting an attribute from each item using attribute=, or applying another filter to each item by passing the filter name as a string. This is the standard Jinja map filter. You can pass any filter by name, including filters that Home Assistant adds, such as as_datetime.

This is one of the most heavily used filters in Home Assistant templates. You will find it in almost every template that works with a collection of 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]. The attribute= form extracts values like .state, .entity_id, or .name from entity state objects returned by expand. The filter form lets you apply conversions like float, int, or round to each item in a list, so you can build filter chains that transform raw entity data into useful results.

Usage

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

As a filter

{{ expand("sensor.temperature_sensors") | map(attribute="state") | list }}

Result (list)

["21.5", "19.8", "22.3"]

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 = are usually required. A few optional parameters have no default value, so the signature shows them without a = as well. To check whether a parameter is required, look at the parameter list below the signature. Each parameter is marked as Required or Optional.

The most common optional parameter without a default value is default. The default parameter sets the value a function returns when the function can’t produce a result, for example, when float gets text that isn’t a number. If you leave out default, there is no fallback value, so most functions raise an error and the template fails. The parameter list of each function says what happens. If you set default, the function returns your value instead.

How to read a signature

Here is the signature of the round filter as an example:

round(
    value: Any,
    precision: int = 0,
    method: str = "common",
    default: Any,
) -> float | int | Any

round is the name of the function.
Between the parentheses are the parameters. Each parameter has a name, followed by a colon and the type of value the parameter expects. The type only tells you what kind of value to pass. For default: Any, you pass a value of any type, such as 0 or "unknown", not the word Any.
= 0 and = "common" are default values. You can leave out precision and method, and round uses these default values.
default has no =, but the parameter list marks default as optional. If you leave out default and round gets a value that isn’t a number, round raises an error.
-> shows the type of value the function returns.
Inside a signature, | means “or”. This function returns a decimal number, a whole number, or the value you passed as default.

round is a filter, so the first parameter, value, is the value before the |. For example, {{ 3.14159 | round(2) }} returns 3.14.

The types you’ll see most often:

str: text, such as "hello"
int: a whole number, such as 5
float: a decimal number, such as 3.14
bool: true or false
list: a list of values, such as [1, 2, 3]. list[str] is a list of texts.
dict: a set of keys and values, such as {"name": "Kitchen"}
datetime and timedelta: a date and time, and a duration. For details, refer to Dates and times.
None: no value
Any: any type of value

Some signatures use special forms:

*args means you can pass any number of values, separated by commas. For example, average(1, 2, 3).
value | name(...) means the function is a filter. The value before the | is passed to the filter as its first parameter. Some filter signatures, like the round example, show this value as the first parameter between the parentheses instead.

map(
    value: list,
    *args: str,
    attribute: str | int | None = None,
    default: Any = None,
) -> iterable

Function parameters

The following parameters can be provided to this filter.

value list Required

The list of items to transform.

args string (Optional)

When extracting attributes, omit this. When applying a filter, pass the filter name as a string (for example, float, int, upper), optionally followed by arguments for that filter.

attribute string (Optional)

The name of the attribute to extract from each item. Supports dotted notation for nested attributes (for example, attributes.brightness). You can also use a number as an index, such as 0 or "items.0".

default any (Optional)

A default value to use when an item does not have the specified attribute. It does not replace an attribute that exists but is set to None. Only used with attribute=.

Extract an attribute from each item

Use attribute= to pull a specific property from each item in the list.

Template: Get entity IDs from expanded group

{{
  expand("light.home_lights")
  | map(attribute="entity_id")
  | list
}}

Result (list)

["light.bedroom", "light.kitchen", "light.living_room"]

Apply a filter to each item

Pass a filter name as a string to apply it to every item in the list.

Template: Convert string values to floats

{{
  ["21.5", "19.8", "22.3"]
  | map("float")
  | list
}}

Result (list)

[21.5, 19.8, 22.3]

Nested attribute access

Use dotted notation to access nested attributes.

Template: Get brightness of all lights that are on

{{
  expand("light.home_lights")
  | selectattr("state", "eq", "on")
  | map(attribute="attributes.brightness")
  | list
}}

Result (list)

[255, 128, 64]

Good to know

Returns an iterable, not a list. Add | list before using it with length, first, or looping twice.
attribute= extracts a property; a filter name as the first positional argument applies that filter to each item. You can use one or the other, not both.
Missing attributes are undefined unless you pass default=. Home Assistant logs a warning when this happens.
default= only replaces missing attributes. To also replace None values, add | map("default", 0, true).
map("float") raises an error on states like unavailable. To avoid this, pass a default: map("float", 0).

Try it yourself

Ready to test this? Open Settings > 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.

Calculate average temperature from a group

Extract state values, convert to floats, and compute the average.

Template

{{
  expand("sensor.temperature_sensors")
  | map(attribute="state")
  | map("float")
  | average
}}

Result (float)

21.2

Get friendly names of all entities in a group

Template

{{
  expand("light.home_lights")
  | map(attribute="name")
  | list
}}

Result (list)

["Bedroom light", "Kitchen light", "Living room light"]

Chain map with round for clean display

Apply multiple transformations by chaining map calls.

Template

{{
  expand("sensor.temperature_sensors")
  | map(attribute="state")
  | map("float")
  | map("round", 1)
  | list
}}

Result (list)

[21.5, 19.8, 22.3]

Apply string filters to a list

Use map to apply string transformations to every item.

Template

{{
  ["hello", "world", "template"]
  | map("upper")
  | list
}}

Result (list)

["HELLO", "WORLD", "TEMPLATE"]

Default value for lights that are off

A light that is off has its brightness attribute set to None. Because the attribute exists, default= does not replace it. Instead, use the default filter with true as the second argument to replace None values.

Template: Brightness with 0 for lights that are off

{{
  expand("light.home_lights")
  | map(attribute="attributes.brightness")
  | map("default", 0, true)
  | list
}}

Result (list)

[255, 0, 128]

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.

Tip

AI assistants like ChatGPT or Claude can also explain or fix templates when you describe what you want in plain language.

Related template functions

These functions work well alongside this one:

Filter items by test: select - Filters a list, keeping only items that pass a given test.
Filter items by attribute test: selectattr - Filters a list, keeping only items where a specified attribute passes a test.
Expand groups into entities: expand - Expands groups and zones into a list of individual entity state objects.
Sort a list: sort - Sorts the items in a list, with optional attribute-based and reverse sorting.

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