Slice a list into sub-lists: slice

The slice filter divides a list into a specified number of sub-lists of approximately equal size. If the items do not divide evenly, the earlier sub-lists will have one more item than the later ones. You can optionally provide a fill value to pad the shorter sub-lists.

This is useful when you need to distribute items evenly across a fixed number of groups. For example, you might want to split a list 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] into columns for display, distribute tasks across multiple workers, or divide a collection into a set number of pages. Note that slice differs from batch: batch creates groups of a fixed size, while slice creates a fixed number of groups.

Usage

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

{{ [1, 2, 3, 4, 5] | slice(3) | list }}

[[1, 2], [3, 4], [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.

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

slice(
    value: list,
    slices: int,
    fill_with: Any = None,
) -> list[list]

Function parameters

The following parameters can be provided to this filter.

Padding with fill_with

Use the fill_with parameter so all sub-lists have the same number of items.

{{ [1, 2, 3, 4, 5] | slice(3, "-") | list }}

[[1, 2], [3, 4], [5, "-"]]

Good to know

• You specify the number of sub-lists, not the size of each one. Use batch when you want a fixed size per group.
• Returns a generator, so add | list before iterating twice.
• Earlier sub-lists get the extra items when the count does not divide evenly.

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.

Distribute entities across columns

Split a list of entities into three columns for a balanced display.

{% set lights = ["light.kitchen", "light.bedroom", "light.hall",
                 "light.porch", "light.garage", "light.office",
                 "light.bathroom"] %}
{% for column in lights | slice(3) %}
  Column {{ loop.index }}: {{ column | join(", ") }}
{% endfor %}

Column 1: light.kitchen, light.bedroom, light.hall
Column 2: light.porch, light.garage, light.office
Column 3: light.bathroom

Split items into two halves

Divide a list into two roughly equal parts.

{% set items = range(8) | list %}
{% set halves = items | slice(2) | list %}
First half: {{ halves[0] | join(", ") }}
Second half: {{ halves[1] | join(", ") }}

First half: 0, 1, 2, 3
Second half: 4, 5, 6, 7

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:

• Split list into batches: batch - Splits a list into smaller batches of a specified size.

• Group items by attribute: groupby - Groups a list of items by a common attribute, producing a list of (grouper, list) pairs.

• Flatten nested lists: flatten - Flattens nested lists into a single flat list.