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Find regex match at index: regex_findall_index

The regex_findall_index template filter finds all occurrences of a regular expression (regex) pattern in a string and returns the match at a specific position (index). A regular expression is a special text pattern that describes what you are looking for. This filter is a shorthand for using regex_findall and then picking one result from the list by its index number.

This is useful when you know a sensor value or text contains multiple matches but you only need one specific one. For example, a sensor might report “23.5C / 45% humidity” and you want only the first number (temperature) or the second number (humidity). The index starts at 0 for the first match, 1 for the second, and so on.

Usage

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

As a filter

{{ "23.5C / 45% humidity" | regex_findall_index("\\d+\\.?\\d*") }}

Result (string)

23.5

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.

regex_findall_index(
    value: str,
    find: str = "",
    index: int = 0,
    ignorecase: bool = False,
) -> str

Function parameters

The following parameters can be provided to this function.

value string Required

The string to search within for matches of the regex pattern.

find string Required

The regular expression pattern to search for. All non-overlapping matches are found, and the one at the specified index is returned.

index integer (Optional, default: 0)

The position of the match to return, starting from 0 for the first match. Defaults to 0 (the first match).

ignorecase boolean (Optional, default: false)

Set to true to make the search case-insensitive.

Selecting different matches

Use the index parameter to pick which match you want from the results.

Template: First and second decimal number

{{
  "10:15 - 23.5C, 11:30 - 24.1C"
  | regex_findall_index("\\d+\\.\\d+", index=0)
}}
{{
  "10:15 - 23.5C, 11:30 - 24.1C"
  | regex_findall_index("\\d+\\.\\d+", index=1)
}}

Result (string)

23.5
24.1

Good to know

Indexing starts at 0 for the first match. Out-of-range indexes raise an error.
Returns the string form of the match. For numbers, convert with float or int afterward.

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.

Extract a specific value from a multi-part sensor

When a sensor returns a combined string with multiple values, pick the one you need.

Template

{% set state = "Power: 150W | Voltage: 230V | Current: 0.65A" %}
Voltage: {{ state | regex_findall_index("\\d+\\.?\\d*", index=1) }}V

Result (string)

Voltage: 230V

Get the second word in a string

Extract the second capitalized word from a status message.

Template

{{
  "Status: Device Online Ready"
  | regex_findall_index("[A-Z][a-z]+", index=1)
}}

Result (string)

Device

Parse a formatted date component

Extract a specific part from a formatted date string.

Template

{% set date_str = "2024-03-15" %}
Month: {{ date_str | regex_findall_index("\\d+", index=1) }}

Result (string)

Month: 03

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:

Find all regex matches: regex_findall - Finds all occurrences of a regular expression pattern in a string and returns them as a list.
Match a regex pattern: regex_match - Tests if a string matches a regular expression pattern at the beginning.
Search for a regex pattern: regex_search - Searches for a regular expression pattern anywhere in a string.
Replace using a regex pattern: regex_replace - Replaces all occurrences of a regular expression pattern in a string.

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