Filters

Filters transform values in template expressions using the pipe syntax.

Basic Usage

{{ name | upper }}
{{ title | truncate(50) }}
{{ items | join(", ") }}

Chaining Filters

{{ name | lower | capitalize }}
{{ text | striptags | truncate(100) }}

Pipeline Operator

Use|>for improved readability:

{{ title |> escape |> upper |> truncate(50) }}

Safe Pipeline (`?|>`)

None-propagating pipeline — if the value is None, all subsequent filters are skipped:

{{ user?.name ?|> upper ?|> trim ?? "Anonymous" }}

Optional Filter (`?|`)

Skip a single filter when the value is None:

{{ value ?| upper ?? "N/A" }}
{{ config?.debug ?| string ?? "unset" }}

Unlike | default("") | upper, ?| preserves falsy values (0, "", False) and only short-circuits onNone.

Common Filters

String Filters

Filter	Description	Example
`upper`	Uppercase	`{{ "hello" \\| upper }}` → `HELLO`
`lower`	Lowercase	`{{ "HELLO" \\| lower }}` → `hello`
`capitalize`	Capitalize first	`{{ "hello" \\| capitalize }}` → `Hello`
`title`	Title case	`{{ "hello world" \\| title }}` → `Hello World`
`trim`	Strip whitespace	`{{ " hi " \\| trim }}` → `hi`
`truncate`	Shorten text	`{{ text \\| truncate(50) }}`
`replace`	Replace text	`{{ s \\| replace("a", "b") }}`
`striptags`	Remove HTML	`{{ html \\| striptags }}`

Collection Filters

Filter	Description	Example
`first`	First item	`{{ items \\| first }}`
`last`	Last item	`{{ items \\| last }}`
`length`	Item count	`{{ items \\| length }}`
`sort`	Sort items	`{{ items \\| sort }}`
`reverse`	Reverse order	`{{ items \\| reverse }}`
`unique`	Remove duplicates	`{{ items \\| unique }}`
`join`	Concatenate	`{{ items \\| join(", ") }}`
`take`	First N items	`{{ items \\| take(5) }}`
`skip`	Skip N items	`{{ items \\| skip(10) }}`

CSS / HTML Filters

Filter	Description	Example
`classes`	Join CSS classes, drop falsy	`{{ ["btn", "", "lg"] \\| classes }}` → `btn lg`
`escape`	HTML escape	`{{ html \\| escape }}`
`safe`	Mark as safe	`{{ trusted \\| safe }}`
`striptags`	Remove tags	`{{ html \\| striptags }}`

Number Filters

Filter	Description	Example
`abs`	Absolute value	`{{ -5 \\| abs }}` → `5`
`decimal`	Fixed decimal places	`{{ 3.14159 \\| decimal(2) }}` → `3.14`
`round`	Round number	`{{ 3.7 \\| round }}` → `4`
`int`	Convert to int	`{{ "42" \\| int }}` → `42`
`float`	Convert to float	`{{ "3.14" \\| float }}` → `3.14`

Utility Filters

Filter	Description	Example
`default`	Fallback value	`{{ x \\| default("N/A") }}`
`tojson`	JSON encode	`{{ data \\| tojson }}` · double-quoted attrs: `{{ cfg \\| tojson(attr=true) }}`
`pprint`	Pretty print	`{{ data \\| pprint }}`
`debug`	Debug output	`{{ items \\| debug }}`

See Filter reference for alltojson parameters (indent, attr, etc.).

Filter Arguments

Filters can accept arguments:

{{ text | truncate(50) }}
{{ text | truncate(50, killwords=true) }}
{{ text | truncate(50, end="...") }}
{{ items | sort(attribute="date", reverse=true) }}

Sorting with Attributes

Sort objects by attribute:

{% for post in posts | sort(attribute="date") %}
    {{ post.title }}
{% end %}

{# Multiple attributes #}
{% for page in pages | sort(attribute="weight,title") %}
    {{ page.title }}
{% end %}

{# Reverse order #}
{% for post in posts | sort(attribute="date", reverse=true) %}
    {{ post.title }}
{% end %}

Grouping

Group items by attribute:

{% for group in posts | groupby("category") %}
    <h2>{{ group.grouper }}</h2>
    {% for post in group.list %}
        {{ post.title }}
    {% end %}
{% end %}

Filtering Items

{# Select items matching condition #}
{{ items | selectattr("is_active") }}
{{ items | selectattr("status", "eq", "published") }}

{# Reject items matching condition #}
{{ items | rejectattr("is_draft") }}

Safe HTML

Mark content as trusted HTML:

{{ html_content | safe }}

{# With reason for code review #}
{{ cms_block | safe(reason="sanitized by bleach library") }}