# filters

URL: /api/environment/filters/
Section: environment

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filters - Kida window.BENGAL_THEME_DEFAULTS = { appearance: 'light', palette: 'brown-bengal' }; window.Bengal = window.Bengal || {}; window.Bengal.enhanceBaseUrl = '/kida/assets/js/enhancements'; window.Bengal.watchDom = true; window.Bengal.debug = false; window.Bengal.enhanceUrls = { 'toc': '/kida/assets/js/enhancements/toc.632a9783.js', 'docs-nav': '/kida/assets/js/enhancements/docs-nav.57e4b129.js', 'tabs': '/kida/assets/js/enhancements/tabs.aac9e817.js', 'lightbox': '/kida/assets/js/enhancements/lightbox.1ca22aa1.js', 'interactive': '/kida/assets/js/enhancements/interactive.fc077855.js', 'mobile-nav': '/kida/assets/js/enhancements/mobile-nav.d991657f.js', 'action-bar': '/kida/assets/js/enhancements/action-bar.d62417f4.js', 'copy-link': '/kida/assets/js/enhancements/copy-link.7d9a5c29.js', 'data-table': '/kida/assets/js/enhancements/data-table.1f5bc1eb.js', 'lazy-loaders': '/kida/assets/js/enhancements/lazy-loaders.a5c38245.js', 'holo': '/kida/assets/js/enhancements/holo.ee13c841.js', 'link-previews': '/kida/assets/js/enhancements/link-previews.8d906535.js' }; (function () { try { var defaults = window.BENGAL_THEME_DEFAULTS || { appearance: 'system', palette: '' }; var defaultAppearance = defaults.appearance; if (defaultAppearance === 'system') { defaultAppearance = (window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches) ? 'dark' : 'light'; } var storedTheme = localStorage.getItem('bengal-theme'); var storedPalette = localStorage.getItem('bengal-palette'); var theme = storedTheme ? (storedTheme === 'system' ? defaultAppearance : storedTheme) : defaultAppearance; var palette = storedPalette ?? defaults.palette; document.documentElement.setAttribute('data-theme', theme); if (palette) { document.documentElement.setAttribute('data-palette', palette); } } catch (e) { document.documentElement.setAttribute('data-theme', 'light'); } })(); { "prerender": [ { "where": { "and": [ { "href_matches": "/docs/*" }, { "not": { "selector_matches": "[data-external], [target=_blank], .external" } } ] }, "eagerness": "conservative" } ], "prefetch": [ { "where": { "and": [ { "href_matches": "/*" }, { "not": { "selector_matches": "[data-external], [target=_blank], .external" } } ] }, "eagerness": "conservative" } ] } Skip to main content Magnifying Glass ESC Recent Clear Magnifying Glass No results for "" Start typing to search... ↑↓ Navigate ↵ Open ESC Close Powered by Lunr )彡 DocumentationInfoAboutArrow ClockwiseGet StartedCodeSyntaxTerminalUsageNoteTutorialsStarburstExtendingBookmarkReferenceTroubleshootingReleasesDevGitHubKida API Reference Magnifying Glass Search ⌘K Palette Appearance Chevron Down Mode Monitor System Sun Light Moon Dark Palette Snow Lynx Brown Bengal Silver Bengal Charcoal Bengal Blue Bengal List )彡 Magnifying Glass Search X Close Documentation Caret Down Info About Arrow Clockwise Get Started Code Syntax Terminal Usage Note Tutorials Starburst Extending Bookmark Reference Troubleshooting Releases Dev Caret Down GitHub Kida API Reference Palette Appearance Chevron Down Mode Monitor System Sun Light Moon Dark Palette Snow Lynx Brown Bengal Silver Bengal Charcoal Bengal Blue Bengal Kida API Reference Caret Right Analysis analyzer cache config dependencies landmarks metadata purity roles Caret Right Compiler Caret Right Statements basic control_flow functions special_blocks template_structure variables _protocols coalescing core expressions utils Caret Right Environment core exceptions filters loaders protocols registry tests Caret Right Parser Caret Right Blocks control_flow core functions special_blocks template_structure variables _protocols core errors expressions statements tokens Caret Right Utils html lru_cache workers _types bytecode_cache kida lexer nodes template tstring Kida API ReferenceEnvironment ᗢ Caret Down Link Copy URL External Open LLM text Copy Copy LLM text Share with AI Ask Claude Ask ChatGPT Ask Gemini Ask Copilot Module environment.filters Built-in filters for Kida templates. Filters transform values in template expressions using the pipe syntax: {{ value | filter }} or {{ value | filter(arg1, arg2) }} Constants for sort key tuples: SORT_KEY_NONE: (1, 0, 0) - Used for None/empty values (sorts last) SORT_KEY_NUMERIC: (0, 0, value) - Used for numeric values SORT_KEY_STRING: (0, 1, value) - Used for string values Categories: String Manipulation: capitalize, lower, upper, title: Case conversion trim/strip: Remove whitespace truncate: Shorten with ellipsis replace, striptags: Text transformation center, indent, wordwrap: Formatting HTML/Security: escape/e: HTML entity encoding (auto-applied with autoescape) safe: Mark content as trusted HTML (skip escaping) striptags: Remove HTML tags Collections: first, last: Get endpoints length/count: Item count sort: Sort sequence (with attribute= for objects) reverse: Reverse order unique: Remove duplicates batch, slice: Group items map, select, reject: Functional operations selectattr, rejectattr: Filter by attribute groupby: Group by attribute join: Concatenate with separator Numbers: abs, round, int, float: Math operations filesizeformat: Human-readable file sizes Type Conversion: string, int, float, list: Type coercion tojson: JSON serialization (auto-escaped) Debugging: debug: Print variable info to stderr pprint: Pretty-print value Validation: default/d: Fallback for None/undefined require: Raise error if None None-Resilient Behavior: Filters handle None gracefully (like Hugo): {{ none | default('N/A') }} -> 'N/A' {{ none | length }} -> 0 {{ none | first }} -> None Custom Filters: >>> env.add_filter('double', lambda x: x * 2) >>> env.add_filter('money', lambda x, currency='$': f'{currency}{x:,.2f}') Or with decorator: >>> @env.filter() ... def reverse_words(s): ... return ' '.join(s.split()[::-1]) 60Functions Functions _make_sort_key_numeric 1 tuple[int, int, int | fl… ▼ Create sort key for numeric value. def _make_sort_key_numeric(value: int | float) -> tuple[int, int, int | float] Parameters Name Type Description value int | float Returns tuple[int, int, int | float] _make_sort_key_string 1 tuple[int, int, str] ▼ Create sort key for string value. def _make_sort_key_string(value: str) -> tuple[int, int, str] Parameters Name Type Description value str Returns tuple[int, int, str] _filter_abs 1 Any ▼ Return absolute value. def _filter_abs(value: Any) -> Any Parameters Name Type Description value Any Returns Any _filter_capitalize 1 str ▼ Capitalize first character. def _filter_capitalize(value: str) -> str Parameters Name Type Description value str Returns str _filter_default 3 Any ▼ Return default if value is undefined or falsy. With None-resilient handling, e… def _filter_default(value: Any, default: Any = '', boolean: bool = False) -> Any Return default if value is undefined or falsy. With None-resilient handling, empty string is treated as missing (like None). This matches Hugo behavior where nil access returns empty string. Parameters Name Type Description value Any default Any Default: '' boolean bool Default: False Returns Any _filter_escape 1 Markup ▼ HTML-escape the value. Returns a Markup object so the result won't be escaped … def _filter_escape(value: Any) -> Markup HTML-escape the value. Returns a Markup object so the result won't be escaped again by autoescape. Uses optimized html_escape_filter from utils.html module. Parameters Name Type Description value Any Returns Markup _filter_first 1 Any ▼ Return first item of sequence. def _filter_first(value: Any) -> Any Parameters Name Type Description value Any Returns Any _filter_int 3 int ▼ Convert to integer. def _filter_int(value: Any, default: int = 0, strict: bool = False) -> int Parameters Name Type Description value Any Value to convert to integer. default int Default value to return if conversion fails (default: 0). Default: 0 strict bool If True, raise TemplateRuntimeError on conversion failure instead of returning default (default: False). Default: False Returns int _filter_join 2 str ▼ Join sequence with separator. def _filter_join(value: Any, separator: str = '') -> str Parameters Name Type Description value Any separator str Default: '' Returns str _filter_last 1 Any ▼ Return last item of sequence. def _filter_last(value: Any) -> Any Parameters Name Type Description value Any Returns Any _filter_length 1 int ▼ Return length of sequence. def _filter_length(value: Any) -> int Parameters Name Type Description value Any Returns int _filter_list 1 list[Any] ▼ Convert to list. def _filter_list(value: Any) -> list[Any] Parameters Name Type Description value Any Returns list[Any] _filter_lower 1 str ▼ Convert to lowercase. def _filter_lower(value: str) -> str Parameters Name Type Description value str Returns str _filter_replace 4 str ▼ Replace occurrences. def _filter_replace(value: str, old: str, new: str, count: int = -1) -> str Parameters Name Type Description value str old str new str count int Default: -1 Returns str _filter_reverse 1 Any ▼ Reverse sequence. def _filter_reverse(value: Any) -> Any Parameters Name Type Description value Any Returns Any _filter_safe 2 Any ▼ Mark value as safe (no HTML escaping). def _filter_safe(value: Any, reason: str | None = None) -> Any Parameters Name Type Description value Any Content to mark as safe for raw HTML output. reason str | None Optional documentation of why this content is trusted. Purely for code review and audit purposes - not used at runtime. Default: None Returns Any _filter_sort 4 list[Any] ▼ Sort sequence with improved error handling for None values. When sorting fails… def _filter_sort(value: Any, reverse: bool = False, case_sensitive: bool = False, attribute: str | None = None) -> list[Any] Sort sequence with improved error handling for None values. When sorting fails due to None comparisons, provides detailed error showing which items have None values for the sort attribute. Parameters Name Type Description value Any reverse bool Default: False case_sensitive bool Default: False attribute str | None Default: None Returns list[Any] _filter_string 1 str ▼ Convert to string. def _filter_string(value: Any) -> str Parameters Name Type Description value Any Returns str _filter_title 1 str ▼ Title case. def _filter_title(value: str) -> str Parameters Name Type Description value str Returns str _filter_trim 2 str ▼ Strip whitespace or specified characters. def _filter_trim(value: str, chars: str | None = None) -> str Parameters Name Type Description value str String to trim chars str | None Optional characters to strip (default: whitespace) Default: None Returns str _filter_truncate 5 str ▼ Truncate string to specified length. def _filter_truncate(value: str, length: int = 255, killwords: bool = False, end: str = '...', leeway: int | None = None) -> str Parameters Name Type Description value str String to truncate length int Maximum length including end marker Default: 255 killwords bool If False (default), truncate at word boundary; if True, cut mid-word Default: False end str String to append when truncated (default: "...") Default: '...' leeway int | None Allow slightly longer strings before truncating (Jinja2 compat, ignored) Default: None Returns str _filter_upper 1 str ▼ Convert to uppercase. def _filter_upper(value: str) -> str Parameters Name Type Description value str Returns str _filter_tojson 2 Any ▼ Convert value to JSON string (marked safe to prevent escaping). def _filter_tojson(value: Any, indent: int | None = None) -> Any Parameters Name Type Description value Any indent int | None Default: None Returns Any _filter_batch 3 list[Any] ▼ Batch items into groups of linecount. def _filter_batch(value: Any, linecount: int, fill_with: Any = None) -> list[Any] Parameters Name Type Description value Any linecount int fill_with Any Default: None Returns list[Any] _filter_slice 3 list[Any] ▼ Slice items into number of groups. def _filter_slice(value: Any, slices: int, fill_with: Any = None) -> list[Any] Parameters Name Type Description value Any slices int fill_with Any Default: None Returns list[Any] _filter_take 2 list[Any] ▼ Take the first N items from a sequence. Kida-native filter for readable pipeli… def _filter_take(value: Any, count: int) -> list[Any] Take the first N items from a sequence. Kida-native filter for readable pipeline operations. Parameters Name Type Description value Any Sequence to take from count int Number of items to take Returns list[Any] _filter_skip 2 list[Any] ▼ Skip the first N items from a sequence. Kida-native filter for readable pipeli… def _filter_skip(value: Any, count: int) -> list[Any] Skip the first N items from a sequence. Kida-native filter for readable pipeline operations. Parameters Name Type Description value Any Sequence to skip from count int Number of items to skip Returns list[Any] _filter_compact 1 list[Any] ▼ Remove None values (and optionally all falsy values) from a sequence. Enables … def _filter_compact(value: Any) -> list[Any] Remove None values (and optionally all falsy values) from a sequence. Enables declarative list building with conditional items, replacing imperative {% do %} patterns. Parameters Name Type Description value Any Sequence to compact Returns list[Any] _filter_map 1 list[Any] ▼ Map an attribute or method from a sequence. def _filter_map(value: Any, *args: Any) -> list[Any] Parameters Name Type Description value Any Returns list[Any] _filter_selectattr 2 list[Any] ▼ Select items where attribute passes test. def _filter_selectattr(value: Any, attr: str, *args: Any) -> list[Any] Parameters Name Type Description value Any attr str Returns list[Any] _filter_rejectattr 2 list[Any] ▼ Reject items where attribute passes test. def _filter_rejectattr(value: Any, attr: str, *args: Any) -> list[Any] Parameters Name Type Description value Any attr str Returns list[Any] _filter_select 2 list[Any] ▼ Select items that pass a test. def _filter_select(value: Any, test_name: str | None = None, *args: Any) -> list[Any] Parameters Name Type Description value Any test_name str | None Default: None Returns list[Any] _filter_reject 2 list[Any] ▼ Reject items that pass a test. def _filter_reject(value: Any, test_name: str | None = None, *args: Any) -> list[Any] Parameters Name Type Description value Any test_name str | None Default: None Returns list[Any] _filter_groupby 2 list[Any] ▼ Group items by attribute with None-safe sorting. Items with None/empty values … def _filter_groupby(value: Any, attribute: str) -> list[Any] Group items by attribute with None-safe sorting. Items with None/empty values for the attribute are grouped together and sorted last. Parameters Name Type Description value Any attribute str Returns list[Any] _filter_striptags 1 str ▼ Strip HTML tags. def _filter_striptags(value: str) -> str Parameters Name Type Description value str Returns str _filter_wordwrap 3 str ▼ Wrap text at width. def _filter_wordwrap(value: str, width: int = 79, break_long_words: bool = True) -> str Parameters Name Type Description value str width int Default: 79 break_long_words bool Default: True Returns str _filter_indent 3 str ▼ Indent text lines. def _filter_indent(value: str, width: int = 4, first: bool = False) -> str Parameters Name Type Description value str width int Default: 4 first bool Default: False Returns str _filter_urlencode 1 str ▼ URL-encode a string. def _filter_urlencode(value: str) -> str Parameters Name Type Description value str Returns str _filter_pprint 1 str ▼ Pretty-print a value. def _filter_pprint(value: Any) -> str Parameters Name Type Description value Any Returns str _filter_xmlattr 1 Markup ▼ Convert dict to XML attributes. Returns Markup to prevent double-escaping when… def _filter_xmlattr(value: dict[str, Any]) -> Markup Convert dict to XML attributes. Returns Markup to prevent double-escaping when autoescape is enabled. Parameters Name Type Description value dict[str, Any] Returns Markup _filter_unique 3 list[Any] ▼ Return unique items. def _filter_unique(value: Any, case_sensitive: bool = False, attribute: str | None = None) -> list[Any] Parameters Name Type Description value Any case_sensitive bool Default: False attribute str | None Default: None Returns list[Any] _filter_min 2 Any ▼ Return minimum value. def _filter_min(value: Any, attribute: str | None = None) -> Any Parameters Name Type Description value Any attribute str | None Default: None Returns Any _filter_max 2 Any ▼ Return maximum value. def _filter_max(value: Any, attribute: str | None = None) -> Any Parameters Name Type Description value Any attribute str | None Default: None Returns Any _filter_sum 3 Any ▼ Return sum of values. def _filter_sum(value: Any, attribute: str | None = None, start: int = 0) -> Any Parameters Name Type Description value Any attribute str | None Default: None start int Default: 0 Returns Any _filter_attr 2 Any ▼ Get attribute from object or dictionary key. Returns "" for None/missing value… def _filter_attr(value: Any, name: str) -> Any Get attribute from object or dictionary key. Returns "" for None/missing values (None-resilient, like Hugo). Parameters Name Type Description value Any name str Returns Any _filter_get 3 Any ▼ Safe dictionary/object access that avoids Python method name conflicts. When a… def _filter_get(value: Any, key: str, default: Any = None) -> Any Safe dictionary/object access that avoids Python method name conflicts. When accessing dict keys like 'items', 'keys', 'values', or 'get', using dotted access (e.g., schema.items) returns the method, not the key value. This filter provides clean syntax for safe key access. Parameters Name Type Description value Any Dict, object, or None to access key str Key or attribute name to access default Any Value to return if key doesn't exist (default: None) Default: None Returns Any _filter_format 1 str ▼ Format string with args/kwargs. def _filter_format(value: str, *args: Any, **kwargs: Any) -> str Parameters Name Type Description value str Returns str _filter_center 2 str ▼ Center string in width. def _filter_center(value: str, width: int = 80) -> str Parameters Name Type Description value str width int Default: 80 Returns str _filter_round 3 float ▼ Round a number to a given precision. def _filter_round(value: Any, precision: int = 0, method: str = 'common') -> float Parameters Name Type Description value Any precision int Default: 0 method str Default: 'common' Returns float _filter_format_number 2 str ▼ Format a number with thousands separators. def _filter_format_number(value: Any, decimal_places: int = 0) -> str Parameters Name Type Description value Any decimal_places int Default: 0 Returns str _filter_commas 1 str ▼ Format a number with commas as thousands separators. Alias for format_number w… def _filter_commas(value: Any) -> str Format a number with commas as thousands separators. Alias for format_number without decimal places. Parameters Name Type Description value Any Returns str _filter_dictsort 4 list[tuple[str, Any]] ▼ Sort a dict and return list of (key, value) pairs. def _filter_dictsort(value: dict[str, Any], case_sensitive: bool = False, by: str = 'key', reverse: bool = False) -> list[tuple[str, Any]] Parameters Name Type Description value dict[str, Any] case_sensitive bool Default: False by str Default: 'key' reverse bool Default: False Returns list[tuple[str, Any]] _filter_wordcount 1 int ▼ Count words in a string. def _filter_wordcount(value: str) -> int Parameters Name Type Description value str Returns int _filter_float 3 float ▼ Convert value to float. def _filter_float(value: Any, default: float = 0.0, strict: bool = False) -> float Parameters Name Type Description value Any Value to convert to float. default float Default value to return if conversion fails (default: 0.0). Default: 0.0 strict bool If True, raise TemplateRuntimeError on conversion failure instead of returning default (default: False). Default: False Returns float _filter_filesizeformat 2 str ▼ Format a file size as human-readable. def _filter_filesizeformat(value: int | float, binary: bool = False) -> str Parameters Name Type Description value int | float binary bool Default: False Returns str _filter_require 3 Any ▼ Require a value to be non-None, raising a clear error if it is. **Usage:** {{ … def _filter_require(value: Any, message: str | None = None, field_name: str | None = None) -> Any Require a value to be non-None, raising a clear error if it is. Usage: {{ user.name | require('User name is required') }} {{ config.api_key | require(field_name='api_key') }} Parameters Name Type Description value Any The value to check message str | None Custom error message if value is None Default: None field_name str | None Field name for the default error message Default: None Returns Any _filter_random 1 Any ▼ Return a random item from the sequence. Warning: This filter is impure (non-de… def _filter_random(value: Any) -> Any Return a random item from the sequence. Warning: This filter is impure (non-deterministic). Parameters Name Type Description value Any A sequence to pick from. Returns Any _filter_shuffle 1 list[Any] ▼ Return a shuffled copy of the sequence. Warning: This filter is impure (non-de… def _filter_shuffle(value: Any) -> list[Any] Return a shuffled copy of the sequence. Warning: This filter is impure (non-deterministic). Parameters Name Type Description value Any A sequence to shuffle. Returns list[Any] _filter_debug 3 Any ▼ Debug filter that prints variable info to stderr and returns the value unchange… def _filter_debug(value: Any, label: str | None = None, max_items: int = 5) -> Any Debug filter that prints variable info to stderr and returns the value unchanged. Usage: {{ posts | debug }} -> Shows type and length {{ posts | debug('my posts') }} -> Shows with custom label {{ posts | debug(max_items=10) }} -> Show more items Output example: DEBUG [my posts]: <list[5]> [0] Page(title='Getting Started', weight=10) [1] Page(title='Installation', weight=None) <-- None! ... Parameters Name Type Description value Any The value to inspect label str | None Optional label for the output Default: None max_items int Maximum number of items to show for sequences Default: 5 Returns Any _debug_repr 2 str ▼ Create a compact repr for debug output. def _debug_repr(value: Any, max_len: int = 60) -> str Parameters Name Type Description value Any max_len int Default: 60 Returns str ← Previous exceptions Next → loaders List © 2026 Kida built in ᓚᘏᗢ { "linkPreviews": { "enabled": true, "hoverDelay": 200, "hideDelay": 150, "showSection": true, "showReadingTime": true, "showWordCount": true, "showDate": true, "showTags": true, "maxTags": 3, "includeSelectors": [".prose"], "excludeSelectors": ["nav", ".toc", ".breadcrumb", ".pagination", ".card", "[class*='-card']", ".tab-nav", "[class*='-widget']", ".child-items", ".content-tiles"], "allowedHosts": [], "allowedSchemes": ["https"], "hostFailureThreshold": 3 } } window.BENGAL_LAZY_ASSETS = { tabulator: '/kida/assets/js/tabulator.min.js', dataTable: '/kida/assets/js/data-table.js', mermaidToolbar: '/kida/assets/js/mermaid-toolbar.9de5abba.js', mermaidTheme: '/kida/assets/js/mermaid-theme.344822c5.js', graphMinimap: '/kida/assets/js/graph-minimap.ff04e939.js', graphContextual: '/kida/assets/js/graph-contextual.355458ba.js' }; window.BENGAL_ICONS = { close: '/kida/assets/icons/close.911d4fe1.svg', enlarge: '/kida/assets/icons/enlarge.652035e5.svg', copy: '/kida/assets/icons/copy.3d56e945.svg', 'download-svg': '/kida/assets/icons/download.04f07e1b.svg', 'download-png': '/kida/assets/icons/image.c34dfd40.svg', 'zoom-in': '/kida/assets/icons/zoom-in.237b4a83.svg', 'zoom-out': '/kida/assets/icons/zoom-out.38857c77.svg', reset: '/kida/assets/icons/reset.d26dba29.svg' }; Arrow Up

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