1 Template Designer Documentation
2 ===============================
4 .. highlight:: html+jinja
6 This document describes the syntax and semantics of the template engine and
7 will be most useful as reference to those creating Jinja templates. As the
8 template engine is very flexible the configuration from the application might
9 be slightly different from here in terms of delimiters and behavior of
16 A template is simply a text file. It can generate any text-based format
17 (HTML, XML, CSV, LaTeX, etc.). It doesn't have a specific extension,
18 ``.html`` or ``.xml`` are just fine.
20 A template contains **variables** or **expressions**, which get replaced with
21 values when the template is evaluated, and tags, which control the logic of
22 the template. The template syntax is heavily inspired by Django and Python.
24 Below is a minimal template that illustrates a few basics. We will cover
25 the details later in that document::
27 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
30 <title>My Webpage</title>
34 {% for item in navigation %}
35 <li><a href="{{ item.href }}">{{ item.caption }}</a></li>
44 This covers the default settings. The application developer might have
45 changed the syntax from ``{% foo %}`` to ``<% foo %>`` or something similar.
47 There are two kinds of delimiters. ``{% ... %}`` and ``{{ ... }}``. The first
48 one is used to execute statements such as for-loops or assign values, the
49 latter prints the result of the expression to the template.
56 The application passes variables to the templates you can mess around in the
57 template. Variables may have attributes or elements on them you can access
58 too. How a variable looks like, heavily depends on the application providing
61 You can use a dot (``.``) to access attributes of a variable, alternative the
62 so-called "subscript" syntax (``[]``) can be used. The following lines do
68 It's important to know that the curly braces are *not* part of the variable
69 but the print statement. If you access variables inside tags don't put the
72 If a variable or attribute does not exist you will get back an undefined
73 value. What you can do with that kind of value depends on the application
74 configuration, the default behavior is that it evaluates to an empty string
75 if printed and that you can iterate over it, but every other operation fails.
77 .. _notes-on-subscriptions:
79 .. admonition:: Implementation
81 For convenience sake ``foo.bar`` in Jinja2 does the following things on
84 - check if there is an attribute called `bar` on `foo`.
85 - if there is not, check if there is an item ``'bar'`` in `foo`.
86 - if there is not, return an undefined object.
88 ``foo['bar']`` on the other hand works mostly the same with the a small
89 difference in the order:
91 - check if there is an item ``'bar'`` in `foo`.
92 - if there is not, check if there is an attribute called `bar` on `foo`.
93 - if there is not, return an undefined object.
95 This is important if an object has an item or attribute with the same
96 name. Additionally there is the :func:`attr` filter that just looks up
104 Variables can be modified by **filters**. Filters are separated from the
105 variable by a pipe symbol (``|``) and may have optional arguments in
106 parentheses. Multiple filters can be chained. The output of one filter is
109 ``{{ name|striptags|title }}`` for example will remove all HTML Tags from the
110 `name` and title-cases it. Filters that accept arguments have parentheses
111 around the arguments, like a function call. This example will join a list
112 by commas: ``{{ list|join(', ') }}``.
114 The :ref:`builtin-filters` below describes all the builtin filters.
121 Beside filters there are also so called "tests" available. Tests can be used
122 to test a variable against a common expression. To test a variable or
123 expression you add `is` plus the name of the test after the variable. For
124 example to find out if a variable is defined you can do ``name is defined``
125 which will then return true or false depending on if `name` is defined.
127 Tests can accept arguments too. If the test only takes one argument you can
128 leave out the parentheses to group them. For example the following two
129 expressions do the same::
131 {% if loop.index is divisibleby 3 %}
132 {% if loop.index is divisibleby(3) %}
134 The :ref:`builtin-tests` below describes all the builtin tests.
140 To comment-out part of a line in a template, use the comment syntax which is
141 by default set to ``{# ... #}``. This is useful to comment out parts of the
142 template for debugging or to add information for other template designers or
145 {# note: disabled template because we no longer use this
146 {% for user in users %}
155 In the default configuration, a single trailing newline is stripped if
156 present, and whitespace is not further modified by the template engine. Each
157 whitespace (spaces, tabs, newlines etc.) is returned unchanged. If the
158 application configures Jinja to `trim_blocks` the first newline after a a
159 template tag is removed automatically (like in PHP).
161 But you can also strip whitespace in templates by hand. If you put an minus
162 sign (``-``) to the start or end of an block (for example a for tag), a
163 comment or variable expression you can remove the whitespaces after or before
166 {% for item in seq -%}
170 This will yield all elements without whitespace between them. If `seq` was
171 a list of numbers from ``1`` to ``9`` the output would be ``123456789``.
173 If :ref:`line-statements` are enabled they strip leading whitespace
174 automatically up to the beginning of the line.
178 You must not use a whitespace between the tag and the minus sign.
182 {%- if foo -%}...{% endif %}
186 {% - if foo - %}...{% endif %}
192 It is sometimes desirable or even necessary to have Jinja ignore parts it
193 would otherwise handle as variables or blocks. For example if the default
194 syntax is used and you want to use ``{{`` as raw string in the template and
195 not start a variable you have to use a trick.
197 The easiest way is to output the variable delimiter (``{{``) by using a
198 variable expression::
202 For bigger sections it makes sense to mark a block `raw`. For example to
203 put Jinja syntax as example into a template you can use this snippet::
207 {% for item in seq %}
219 If line statements are enabled by the application it's possible to mark a
220 line as a statement. For example if the line statement prefix is configured
221 to ``#`` the following two examples are equivalent::
230 {% for item in seq %}
235 The line statement prefix can appear anywhere on the line as long as no text
236 precedes it. For better readability statements that start a block (such as
237 `for`, `if`, `elif` etc.) may end with a colon::
246 Line statements can span multiple lines if there are open parentheses,
250 # for href, caption in [('index.html', 'Index'),
251 ('about.html', 'About')]:
252 <li><a href="{{ href }}">{{ caption }}</a></li>
256 Since Jinja 2.2 line-based comments are available as well. For example if
257 the line-comment prefix is configured to be ``##`` everything from ``##`` to
258 the end of the line is ignored (excluding the newline sign)::
261 <li>{{ item }}</li> ## this comment is ignored
265 .. _template-inheritance:
270 The most powerful part of Jinja is template inheritance. Template inheritance
271 allows you to build a base "skeleton" template that contains all the common
272 elements of your site and defines **blocks** that child templates can override.
274 Sounds complicated but is very basic. It's easiest to understand it by starting
281 This template, which we'll call ``base.html``, defines a simple HTML skeleton
282 document that you might use for a simple two-column page. It's the job of
283 "child" templates to fill the empty blocks with content::
285 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
287 <html xmlns="http://www.w3.org/1999/xhtml">
290 <link rel="stylesheet" href="style.css" />
291 <title>{% block title %}{% endblock %} - My Webpage</title>
295 <div id="content">{% block content %}{% endblock %}</div>
298 © Copyright 2008 by <a href="http://domain.invalid/">you</a>.
303 In this example, the ``{% block %}`` tags define four blocks that child templates
304 can fill in. All the `block` tag does is to tell the template engine that a
305 child template may override those portions of the template.
310 A child template might look like this::
312 {% extends "base.html" %}
313 {% block title %}Index{% endblock %}
316 <style type="text/css">
317 .important { color: #336699; }
322 <p class="important">
323 Welcome on my awesome homepage.
327 The ``{% extends %}`` tag is the key here. It tells the template engine that
328 this template "extends" another template. When the template system evaluates
329 this template, first it locates the parent. The extends tag should be the
330 first tag in the template. Everything before it is printed out normally and
331 may cause confusion. For details about this behavior and how to take
332 advantage of it, see :ref:`null-master-fallback`.
334 The filename of the template depends on the template loader. For example the
335 :class:`FileSystemLoader` allows you to access other templates by giving the
336 filename. You can access templates in subdirectories with a slash::
338 {% extends "layout/default.html" %}
340 But this behavior can depend on the application embedding Jinja. Note that
341 since the child template doesn't define the ``footer`` block, the value from
342 the parent template is used instead.
344 You can't define multiple ``{% block %}`` tags with the same name in the
345 same template. This limitation exists because a block tag works in "both"
346 directions. That is, a block tag doesn't just provide a hole to fill - it
347 also defines the content that fills the hole in the *parent*. If there
348 were two similarly-named ``{% block %}`` tags in a template, that template's
349 parent wouldn't know which one of the blocks' content to use.
351 If you want to print a block multiple times you can however use the special
352 `self` variable and call the block with that name::
354 <title>{% block title %}{% endblock %}</title>
355 <h1>{{ self.title() }}</h1>
356 {% block body %}{% endblock %}
362 It's possible to render the contents of the parent block by calling `super`.
363 This gives back the results of the parent block::
366 <h3>Table Of Contents</h3>
375 Jinja2 allows you to put the name of the block after the end tag for better
379 {% block inner_sidebar %}
381 {% endblock inner_sidebar %}
382 {% endblock sidebar %}
384 However the name after the `endblock` word must match the block name.
387 Block Nesting and Scope
388 ~~~~~~~~~~~~~~~~~~~~~~~
390 Blocks can be nested for more complex layouts. However per default blocks
391 may not access variables from outer scopes::
393 {% for item in seq %}
394 <li>{% block loop_item %}{{ item }}{% endblock %}</li>
397 This example would output empty ``<li>`` items because `item` is unavailable
398 inside the block. The reason for this is that if the block is replaced by
399 a child template a variable would appear that was not defined in the block or
400 passed to the context.
402 Starting with Jinja 2.2 you can explicitly specify that variables are
403 available in a block by setting the block to "scoped" by adding the `scoped`
404 modifier to a block declaration::
406 {% for item in seq %}
407 <li>{% block loop_item scoped %}{{ item }}{% endblock %}</li>
410 When overriding a block the `scoped` modifier does not have to be provided.
416 .. versionchanged:: 2.4
418 If a template object was passed to the template context you can
419 extend from that object as well. Assuming the calling code passes
420 a layout template as `layout_template` to the environment, this
423 {% extends layout_template %}
425 Previously the `layout_template` variable had to be a string with
426 the layout template's filename for this to work.
432 When generating HTML from templates, there's always a risk that a variable will
433 include characters that affect the resulting HTML. There are two approaches:
434 manually escaping each variable or automatically escaping everything by default.
436 Jinja supports both, but what is used depends on the application configuration.
437 The default configuaration is no automatic escaping for various reasons:
439 - escaping everything except of safe values will also mean that Jinja is
440 escaping variables known to not include HTML such as numbers which is
441 a huge performance hit.
443 - The information about the safety of a variable is very fragile. It could
444 happen that by coercing safe and unsafe values the return value is double
447 Working with Manual Escaping
448 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
450 If manual escaping is enabled it's **your** responsibility to escape
451 variables if needed. What to escape? If you have a variable that *may*
452 include any of the following chars (``>``, ``<``, ``&``, or ``"``) you
453 **have to** escape it unless the variable contains well-formed and trusted
454 HTML. Escaping works by piping the variable through the ``|e`` filter:
455 ``{{ user.username|e }}``.
457 Working with Automatic Escaping
458 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
460 When automatic escaping is enabled everything is escaped by default except
461 for values explicitly marked as safe. Those can either be marked by the
462 application or in the template by using the `|safe` filter. The main
463 problem with this approach is that Python itself doesn't have the concept
464 of tainted values so the information if a value is safe or unsafe can get
465 lost. If the information is lost escaping will take place which means that
466 you could end up with double escaped contents.
468 Double escaping is easy to avoid however, just rely on the tools Jinja2
469 provides and don't use builtin Python constructs such as the string modulo
472 Functions returning template data (macros, `super`, `self.BLOCKNAME`) return
475 String literals in templates with automatic escaping are considered unsafe
476 too. The reason for this is that the safe string is an extension to Python
477 and not every library will work properly with it.
480 List of Control Structures
481 --------------------------
483 A control structure refers to all those things that control the flow of a
484 program - conditionals (i.e. if/elif/else), for-loops, as well as things like
485 macros and blocks. Control structures appear inside ``{% ... %}`` blocks
486 in the default syntax.
491 Loop over each item in a sequence. For example, to display a list of users
492 provided in a variable called `users`::
496 {% for user in users %}
497 <li>{{ user.username|e }}</li>
501 As variables in templates retain their object properties, it is possible to
502 iterate over containers like `dict`::
505 {% for key, value in my_dict.iteritems() %}
507 <dd>{{ value|e }}</dd>
511 Note however that dictionaries usually are unordered so you might want to
512 either pass it as a sorted list to the template or use the `dictsort`
515 Inside of a for-loop block you can access some special variables:
517 +-----------------------+---------------------------------------------------+
518 | Variable | Description |
519 +=======================+===================================================+
520 | `loop.index` | The current iteration of the loop. (1 indexed) |
521 +-----------------------+---------------------------------------------------+
522 | `loop.index0` | The current iteration of the loop. (0 indexed) |
523 +-----------------------+---------------------------------------------------+
524 | `loop.revindex` | The number of iterations from the end of the loop |
526 +-----------------------+---------------------------------------------------+
527 | `loop.revindex0` | The number of iterations from the end of the loop |
529 +-----------------------+---------------------------------------------------+
530 | `loop.first` | True if first iteration. |
531 +-----------------------+---------------------------------------------------+
532 | `loop.last` | True if last iteration. |
533 +-----------------------+---------------------------------------------------+
534 | `loop.length` | The number of items in the sequence. |
535 +-----------------------+---------------------------------------------------+
536 | `loop.cycle` | A helper function to cycle between a list of |
537 | | sequences. See the explanation below. |
538 +-----------------------+---------------------------------------------------+
540 Within a for-loop, it's possible to cycle among a list of strings/variables
541 each time through the loop by using the special `loop.cycle` helper::
543 {% for row in rows %}
544 <li class="{{ loop.cycle('odd', 'even') }}">{{ row }}</li>
547 Since Jinja 2.1 an extra `cycle` helper exists that allows loop-unbound
548 cycling. For more information have a look at the :ref:`builtin-globals`.
552 Unlike in Python it's not possible to `break` or `continue` in a loop. You
553 can however filter the sequence during iteration which allows you to skip
554 items. The following example skips all the users which are hidden::
556 {% for user in users if not user.hidden %}
557 <li>{{ user.username|e }}</li>
560 The advantage is that the special `loop` variable will count correctly thus
561 not counting the users not iterated over.
563 If no iteration took place because the sequence was empty or the filtering
564 removed all the items from the sequence you can render a replacement block
568 {% for user in users %}
569 <li>{{ user.username|e }}</li>
571 <li><em>no users found</em></li>
575 It is also possible to use loops recursively. This is useful if you are
576 dealing with recursive data such as sitemaps. To use loops recursively you
577 basically have to add the `recursive` modifier to the loop definition and
578 call the `loop` variable with the new iterable where you want to recurse.
580 The following example implements a sitemap with recursive loops::
583 {%- for item in sitemap recursive %}
584 <li><a href="{{ item.href|e }}">{{ item.title }}</a>
585 {%- if item.children -%}
586 <ul class="submenu">{{ loop(item.children) }}</ul>
595 The `if` statement in Jinja is comparable with the if statements of Python.
596 In the simplest form you can use it to test if a variable is defined, not
601 {% for user in users %}
602 <li>{{ user.username|e }}</li>
607 For multiple branches `elif` and `else` can be used like in Python. You can
608 use more complex :ref:`expressions` there too::
612 {% elif kenny.dead %}
613 You killed Kenny! You bastard!!!
615 Kenny looks okay --- so far
618 If can also be used as :ref:`inline expression <if-expression>` and for
619 :ref:`loop filtering <loop-filtering>`.
625 Macros are comparable with functions in regular programming languages. They
626 are useful to put often used idioms into reusable functions to not repeat
629 Here a small example of a macro that renders a form element::
631 {% macro input(name, value='', type='text', size=20) -%}
632 <input type="{{ type }}" name="{{ name }}" value="{{
633 value|e }}" size="{{ size }}">
636 The macro can then be called like a function in the namespace::
638 <p>{{ input('username') }}</p>
639 <p>{{ input('password', type='password') }}</p>
641 If the macro was defined in a different template you have to
642 :ref:`import <import>` it first.
644 Inside macros you have access to three special variables:
647 If more positional arguments are passed to the macro than accepted by the
648 macro they end up in the special `varargs` variable as list of values.
651 Like `varargs` but for keyword arguments. All unconsumed keyword
652 arguments are stored in this special variable.
655 If the macro was called from a :ref:`call<call>` tag the caller is stored
656 in this variable as macro which can be called.
658 Macros also expose some of their internal details. The following attributes
659 are available on a macro object:
662 The name of the macro. ``{{ input.name }}`` will print ``input``.
665 A tuple of the names of arguments the macro accepts.
668 A tuple of default values.
671 This is `true` if the macro accepts extra keyword arguments (ie: accesses
672 the special `kwargs` variable).
675 This is `true` if the macro accepts extra positional arguments (ie:
676 accesses the special `varargs` variable).
679 This is `true` if the macro accesses the special `caller` variable and may
680 be called from a :ref:`call<call>` tag.
682 If a macro name starts with an underscore it's not exported and can't
691 In some cases it can be useful to pass a macro to another macro. For this
692 purpose you can use the special `call` block. The following example shows
693 a macro that takes advantage of the call functionality and how it can be
696 {% macro render_dialog(title, class='dialog') -%}
697 <div class="{{ class }}">
699 <div class="contents">
705 {% call render_dialog('Hello World') %}
706 This is a simple dialog rendered by using a macro and
710 It's also possible to pass arguments back to the call block. This makes it
711 useful as replacement for loops. Generally speaking a call block works
712 exactly like an macro, just that it doesn't have a name.
714 Here an example of how a call block can be used with arguments::
716 {% macro dump_users(users) -%}
718 {%- for user in users %}
719 <li><p>{{ user.username|e }}</p>{{ caller(user) }}</li>
724 {% call(user) dump_users(list_of_user) %}
727 <dd>{{ user.realname|e }}</dd>
729 <dd>{{ user.description }}</dd>
737 Filter sections allow you to apply regular Jinja2 filters on a block of
738 template data. Just wrap the code in the special `filter` section::
741 This text becomes uppercase
748 Inside code blocks you can also assign values to variables. Assignments at
749 top level (outside of blocks, macros or loops) are exported from the template
750 like top level macros and can be imported by other templates.
752 Assignments use the `set` tag and can have multiple targets::
754 {% set navigation = [('index.html', 'Index'), ('about.html', 'About')] %}
755 {% set key, value = call_something() %}
761 The `extends` tag can be used to extend a template from another one. You
762 can have multiple of them in a file but only one of them may be executed
763 at the time. See the section about :ref:`template-inheritance` above.
769 Blocks are used for inheritance and act as placeholders and replacements
770 at the same time. They are documented in detail as part of the section
771 about :ref:`template-inheritance`.
777 The `include` statement is useful to include a template and return the
778 rendered contents of that file into the current namespace::
780 {% include 'header.html' %}
782 {% include 'footer.html' %}
784 Included templates have access to the variables of the active context by
785 default. For more details about context behavior of imports and includes
786 see :ref:`import-visibility`.
788 From Jinja 2.2 onwards you can mark an include with ``ignore missing`` in
789 which case Jinja will ignore the statement if the template to be ignored
790 does not exist. When combined with ``with`` or ``without context`` it has
791 to be placed *before* the context visibility statement. Here some valid
794 {% include "sidebar.html" ignore missing %}
795 {% include "sidebar.html" ignore missing with context %}
796 {% include "sidebar.html" ignore missing without context %}
798 .. versionadded:: 2.2
800 You can also provide a list of templates that are checked for existence
801 before inclusion. The first template that exists will be included. If
802 `ignore missing` is given, it will fall back to rendering nothing if
803 none of the templates exist, otherwise it will raise an exception.
807 {% include ['page_detailed.html', 'page.html'] %}
808 {% include ['special_sidebar.html', 'sidebar.html'] ignore missing %}
810 .. versionchanged:: 2.4
811 If a template object was passed to the template context you can
812 include that object using `include`.
819 Jinja2 supports putting often used code into macros. These macros can go into
820 different templates and get imported from there. This works similar to the
821 import statements in Python. It's important to know that imports are cached
822 and imported templates don't have access to the current template variables,
823 just the globals by default. For more details about context behavior of
824 imports and includes see :ref:`import-visibility`.
826 There are two ways to import templates. You can import the complete template
827 into a variable or request specific macros / exported variables from it.
829 Imagine we have a helper module that renders forms (called `forms.html`)::
831 {% macro input(name, value='', type='text') -%}
832 <input type="{{ type }}" value="{{ value|e }}" name="{{ name }}">
835 {%- macro textarea(name, value='', rows=10, cols=40) -%}
836 <textarea name="{{ name }}" rows="{{ rows }}" cols="{{ cols
837 }}">{{ value|e }}</textarea>
840 The easiest and most flexible is importing the whole module into a variable.
841 That way you can access the attributes::
843 {% import 'forms.html' as forms %}
846 <dd>{{ forms.input('username') }}</dd>
848 <dd>{{ forms.input('password', type='password') }}</dd>
850 <p>{{ forms.textarea('comment') }}</p>
853 Alternatively you can import names from the template into the current
856 {% from 'forms.html' import input as input_field, textarea %}
859 <dd>{{ input_field('username') }}</dd>
861 <dd>{{ input_field('password', type='password') }}</dd>
863 <p>{{ textarea('comment') }}</p>
865 Macros and variables starting with one ore more underscores are private and
868 .. versionchanged:: 2.4
869 If a template object was passed to the template context you can
870 import from that object.
873 .. _import-visibility:
875 Import Context Behavior
876 -----------------------
878 Per default included templates are passed the current context and imported
879 templates not. The reason for this is that imports unlike includes are
880 cached as imports are often used just as a module that holds macros.
882 This however can be changed of course explicitly. By adding `with context`
883 or `without context` to the import/include directive the current context
884 can be passed to the template and caching is disabled automatically.
888 {% from 'forms.html' import input with context %}
889 {% include 'header.html' without context %}
893 In Jinja 2.0 the context that was passed to the included template
894 did not include variables defined in the template. As a matter of
895 fact this did not work::
897 {% for box in boxes %}
898 {% include "render_box.html" %}
901 The included template ``render_box.html`` is *not* able to access
902 `box` in Jinja 2.0. As of Jinja 2.1 ``render_box.html`` *is* able
911 Jinja allows basic expressions everywhere. These work very similar to regular
912 Python and even if you're not working with Python you should feel comfortable
918 The simplest form of expressions are literals. Literals are representations
919 for Python objects such as strings and numbers. The following literals exist:
922 Everything between two double or single quotes is a string. They are
923 useful whenever you need a string in the template (for example as
924 arguments to function calls, filters or just to extend or include a
928 Integers and floating point numbers are created by just writing the
929 number down. If a dot is present the number is a float, otherwise an
930 integer. Keep in mind that for Python ``42`` and ``42.0`` is something
933 ['list', 'of', 'objects']:
934 Everything between two brackets is a list. Lists are useful to store
935 sequential data in or to iterate over them. For example you can easily
936 create a list of links using lists and tuples with a for loop::
939 {% for href, caption in [('index.html', 'Index'), ('about.html', 'About'),
940 ('downloads.html', 'Downloads')] %}
941 <li><a href="{{ href }}">{{ caption }}</a></li>
945 ('tuple', 'of', 'values'):
946 Tuples are like lists, just that you can't modify them. If the tuple
947 only has one item you have to end it with a comma. Tuples are usually
948 used to represent items of two or more elements. See the example above
951 {'dict': 'of', 'key': 'and', 'value': 'pairs'}:
952 A dict in Python is a structure that combines keys and values. Keys must
953 be unique and always have exactly one value. Dicts are rarely used in
954 templates, they are useful in some rare cases such as the :func:`xmlattr`
958 true is always true and false is always false.
962 The special constants `true`, `false` and `none` are indeed lowercase.
963 Because that caused confusion in the past, when writing `True` expands
964 to an undefined variable that is considered false, all three of them can
965 be written in title case too (`True`, `False`, and `None`). However for
966 consistency (all Jinja identifiers are lowercase) you should use the
972 Jinja allows you to calculate with values. This is rarely useful in templates
973 but exists for completeness' sake. The following operators are supported:
976 Adds two objects together. Usually the objects are numbers but if both are
977 strings or lists you can concatenate them this way. This however is not
978 the preferred way to concatenate strings! For string concatenation have
979 a look at the ``~`` operator. ``{{ 1 + 1 }}`` is ``2``.
982 Substract the second number from the first one. ``{{ 3 - 2 }}`` is ``1``.
985 Divide two numbers. The return value will be a floating point number.
986 ``{{ 1 / 2 }}`` is ``{{ 0.5 }}``.
989 Divide two numbers and return the truncated integer result.
990 ``{{ 20 // 7 }}`` is ``2``.
993 Calculate the remainder of an integer division. ``{{ 11 % 7 }}`` is ``4``.
996 Multiply the left operand with the right one. ``{{ 2 * 2 }}`` would
997 return ``4``. This can also be used to repeat a string multiple times.
998 ``{{ '=' * 80 }}`` would print a bar of 80 equal signs.
1001 Raise the left operand to the power of the right operand. ``{{ 2**3 }}``
1008 Compares two objects for equality.
1011 Compares two objects for inequality.
1014 `true` if the left hand side is greater than the right hand side.
1017 `true` if the left hand side is greater or equal to the right hand side.
1020 `true` if the left hand side is lower than the right hand side.
1023 `true` if the left hand side is lower or equal to the right hand side.
1028 For `if` statements, `for` filtering or `if` expressions it can be useful to
1029 combine multiple expressions:
1032 Return true if the left and the right operand is true.
1035 Return true if the left or the right operand is true.
1038 negate a statement (see below).
1041 group an expression.
1043 .. admonition:: Note
1045 The ``is`` and ``in`` operators support negation using an infix notation
1046 too: ``foo is not bar`` and ``foo not in bar`` instead of ``not foo is bar``
1047 and ``not foo in bar``. All other expressions require a prefix notation:
1048 ``not (foo and bar).``
1054 The following operators are very useful but don't fit into any of the other
1058 Perform sequence / mapping containment test. Returns true if the left
1059 operand is contained in the right. ``{{ 1 in [1, 2, 3] }}`` would for
1060 example return true.
1063 Performs a :ref:`test <tests>`.
1066 Applies a :ref:`filter <filters>`.
1069 Converts all operands into strings and concatenates them.
1070 ``{{ "Hello " ~ name ~ "!" }}`` would return (assuming `name` is
1071 ``'John'``) ``Hello John!``.
1074 Call a callable: ``{{ post.render() }}``. Inside of the parentheses you
1075 can use positional arguments and keyword arguments like in python:
1076 ``{{ post.render(user, full=true) }}``.
1079 Get an attribute of an object. (See :ref:`variables`)
1087 It is also possible to use inline `if` expressions. These are useful in some
1088 situations. For example you can use this to extend from one template if a
1089 variable is defined, otherwise from the default layout template::
1091 {% extends layout_template if layout_template is defined else 'master.html' %}
1093 The general syntax is ``<do something> if <something is true> else <do
1096 The `else` part is optional. If not provided the else block implicitly
1097 evaluates into an undefined object::
1099 {{ '[%s]' % page.title if page.title }}
1102 .. _builtin-filters:
1104 List of Builtin Filters
1105 -----------------------
1112 List of Builtin Tests
1113 ---------------------
1117 .. _builtin-globals:
1119 List of Global Functions
1120 ------------------------
1122 The following functions are available in the global scope by default:
1124 .. function:: range([start,] stop[, step])
1126 Return a list containing an arithmetic progression of integers.
1127 range(i, j) returns [i, i+1, i+2, ..., j-1]; start (!) defaults to 0.
1128 When step is given, it specifies the increment (or decrement).
1129 For example, range(4) returns [0, 1, 2, 3]. The end point is omitted!
1130 These are exactly the valid indices for a list of 4 elements.
1132 This is useful to repeat a template block multiple times for example
1133 to fill a list. Imagine you have 7 users in the list but you want to
1134 render three empty items to enforce a height with CSS::
1137 {% for user in users %}
1138 <li>{{ user.username }}</li>
1140 {% for number in range(10 - users|count) %}
1141 <li class="empty"><span>...</span></li>
1145 .. function:: lipsum(n=5, html=True, min=20, max=100)
1147 Generates some lorem ipsum for the template. Per default five paragraphs
1148 with HTML are generated each paragraph between 20 and 100 words. If html
1149 is disabled regular text is returned. This is useful to generate simple
1150 contents for layout testing.
1152 .. function:: dict(\**items)
1154 A convenient alternative to dict literals. ``{'foo': 'bar'}`` is the same
1155 as ``dict(foo='bar')``.
1157 .. class:: cycler(\*items)
1159 The cycler allows you to cycle among values similar to how `loop.cycle`
1160 works. Unlike `loop.cycle` however you can use this cycler outside of
1161 loops or over multiple loops.
1163 This is for example very useful if you want to show a list of folders and
1164 files, with the folders on top, but both in the same list with alternating
1167 The following example shows how `cycler` can be used::
1169 {% set row_class = cycler('odd', 'even') %}
1170 <ul class="browser">
1171 {% for folder in folders %}
1172 <li class="folder {{ row_class.next() }}">{{ folder|e }}</li>
1174 {% for filename in files %}
1175 <li class="file {{ row_class.next() }}">{{ filename|e }}</li>
1179 A cycler has the following attributes and methods:
1183 Resets the cycle to the first item.
1187 Goes one item a head and returns the then current item.
1189 .. attribute:: current
1191 Returns the current item.
1193 **new in Jinja 2.1**
1195 .. class:: joiner(sep=', ')
1197 A tiny helper that can be use to "join" multiple sections. A joiner is
1198 passed a string and will return that string every time it's called, except
1199 the first time in which situation it returns an empty string. You can
1200 use this to join things::
1202 {% set pipe = joiner("|") %}
1203 {% if categories %} {{ pipe() }}
1204 Categories: {{ categories|join(", ") }}
1206 {% if author %} {{ pipe() }}
1207 Author: {{ author() }}
1209 {% if can_edit %} {{ pipe() }}
1210 <a href="?action=edit">Edit</a>
1213 **new in Jinja 2.1**
1219 The following sections cover the built-in Jinja2 extensions that may be
1220 enabled by the application. The application could also provide further
1221 extensions not covered by this documentation. In that case there should
1222 be a separate document explaining the extensions.
1224 .. _i18n-in-templates:
1229 If the i18n extension is enabled it's possible to mark parts in the template
1230 as translatable. To mark a section as translatable you can use `trans`::
1232 <p>{% trans %}Hello {{ user }}!{% endtrans %}</p>
1234 To translate a template expression --- say, using template filters or just
1235 accessing an attribute of an object --- you need to bind the expression to a
1236 name for use within the translation block::
1238 <p>{% trans user=user.username %}Hello {{ user }}!{% endtrans %}</p>
1240 If you need to bind more than one expression inside a `trans` tag, separate
1241 the pieces with a comma (``,``)::
1243 {% trans book_title=book.title, author=author.name %}
1244 This is {{ book_title }} by {{ author }}
1247 Inside trans tags no statements are allowed, only variable tags are.
1249 To pluralize, specify both the singular and plural forms with the `pluralize`
1250 tag, which appears between `trans` and `endtrans`::
1252 {% trans count=list|length %}
1253 There is {{ count }} {{ name }} object.
1255 There are {{ count }} {{ name }} objects.
1258 Per default the first variable in a block is used to determine the correct
1259 singular or plural form. If that doesn't work out you can specify the name
1260 which should be used for pluralizing by adding it as parameter to `pluralize`::
1262 {% trans ..., user_count=users|length %}...
1263 {% pluralize user_count %}...{% endtrans %}
1265 It's also possible to translate strings in expressions. For that purpose
1266 three functions exist:
1268 _ `gettext`: translate a single string
1269 - `ngettext`: translate a pluralizable string
1270 - `_`: alias for `gettext`
1272 For example you can print a translated string easily this way::
1274 {{ _('Hello World!') }}
1276 To use placeholders you can use the `format` filter::
1278 {{ _('Hello %(user)s!')|format(user=user.username) }}
1280 For multiple placeholders always use keyword arguments to `format` as other
1281 languages may not use the words in the same order.
1283 .. versionchanged:: 2.5
1285 If newstyle gettext calls are activated (:ref:`newstyle-gettext`), using
1286 placeholders is a lot easier:
1288 .. sourcecode:: html+jinja
1290 {{ gettext('Hello World!') }}
1291 {{ gettext('Hello %(name)s!', name='World') }}
1292 {{ ngettext('%(num)d apple', '%(num)d apples', apples|count) }}
1294 Note that the `ngettext` function's format string automatically receives
1295 the count as `num` parameter additionally to the regular parameters.
1298 Expression Statement
1299 ~~~~~~~~~~~~~~~~~~~~
1301 If the expression-statement extension is loaded a tag called `do` is available
1302 that works exactly like the regular variable expression (``{{ ... }}``) just
1303 that it doesn't print anything. This can be used to modify lists::
1305 {% do navigation.append('a string') %}
1311 If the application enables the :ref:`loopcontrols-extension` it's possible to
1312 use `break` and `continue` in loops. When `break` is reached, the loop is
1313 terminated; if `continue` is reached, the processing is stopped and continues
1314 with the next iteration.
1316 Here a loop that skips every second item::
1318 {% for user in users %}
1319 {%- if loop.index is even %}{% continue %}{% endif %}
1323 Likewise a look that stops processing after the 10th iteration::
1325 {% for user in users %}
1326 {%- if loop.index >= 10 %}{% break %}{% endif %}
1333 .. versionadded:: 2.3
1335 If the application enables the :ref:`with-extension` it is possible to
1336 use the `with` keyword in templates. This makes it possible to create
1337 a new inner scope. Variables set within this scope are not visible
1338 outside of the scope.
1340 With in a nutshell::
1344 {{ foo }} foo is 42 here
1346 foo is not visible here any longer
1348 Because it is common to set variables at the beginning of the scope
1349 you can do that within the with statement. The following two examples
1361 .. _autoescape-overrides:
1363 Autoescape Extension
1364 --------------------
1366 .. versionadded:: 2.4
1368 If the application enables the :ref:`autoescape-extension` one can
1369 activate and deactivate the autoescaping from within the templates.
1373 {% autoescape true %}
1374 Autoescaping is active within this block
1377 {% autoescape false %}
1378 Autoescaping is inactive within this block
1381 After the `endautoescape` the behavior is reverted to what it was before.