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 delimiers. ``{% ... %}`` 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 by 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 spaces: ``{{ 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 user this
146 {% for user in users %}
155 In the default configuration whitespace is not further modified by the
156 template engine, so each whitespace (spaces, tabs, newlines etc.) is returned
157 unchanged. If the application configures Jinja to `trim_blocks` the first
158 newline after a a template tag is removed automatically (like in PHP).
160 But you can also strip whitespace in templates by hand. If you put an minus
161 sign (``-``) to the start or end of an block (for example a for tag), a
162 comment or variable expression you can remove the whitespaces after or before
165 {% for item in seq -%}
169 This will yield all elements without whitespace between them. If `seq` was
170 a list of numbers from ``1`` to ``9`` the output would be ``123456789``.
172 If :ref:`line-statements` are enabled they strip leading whitespace
173 automatically up to the beginning of the line.
177 You must not use a whitespace between the tag and the minus sign.
181 {%- if foo -%}...{% endif %}
185 {% - if foo - %}...{% endif %}
191 It is sometimes desirable or even necessary to have Jinja ignore parts it
192 would otherwise handle as variables or blocks. For example if the default
193 syntax is used and you want to use ``{{`` as raw string in the template and
194 not start a variable you have to use a trick.
196 The easiest way is to output the variable delimiter (``{{``) by using a
197 variable expression::
201 For bigger sections it makes sense to mark a block `raw`. For example to
202 put Jinja syntax as example into a template you can use this snippet::
206 {% for item in seq %}
218 If line statements are enabled by the application it's possible to mark a
219 line as a statement. For example if the line statement prefix is configured
220 to ``#`` the following two examples are equivalent::
229 {% for item in seq %}
234 The line statement prefix can appear anywhere on the line as long as no text
235 precedes it. For better readability statements that start a block (such as
236 `for`, `if`, `elif` etc.) may end with a colon::
245 Line statements can span multiple lines if there are open parentheses,
249 # for href, caption in [('index.html', 'Index'),
250 ('about.html', 'About')]:
251 <li><a href="{{ href }}">{{ caption }}</a></li>
256 .. _template-inheritance:
261 The most powerful part of Jinja is template inheritance. Template inheritance
262 allows you to build a base "skeleton" template that contains all the common
263 elements of your site and defines **blocks** that child templates can override.
265 Sounds complicated but is very basic. It's easiest to understand it by starting
272 This template, which we'll call ``base.html``, defines a simple HTML skeleton
273 document that you might use for a simple two-column page. It's the job of
274 "child" templates to fill the empty blocks with content::
276 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
278 <html xmlns="http://www.w3.org/1999/xhtml">
281 <link rel="stylesheet" href="style.css" />
282 <title>{% block title %}{% endblock %} - My Webpage</title>
286 <div id="content">{% block content %}{% endblock %}</div>
289 © Copyright 2008 by <a href="http://domain.invalid/">you</a>.
294 In this example, the ``{% block %}`` tags define four blocks that child templates
295 can fill in. All the `block` tag does is to tell the template engine that a
296 child template may override those portions of the template.
301 A child template might look like this::
303 {% extends "base.html" %}
304 {% block title %}Index{% endblock %}
307 <style type="text/css">
308 .important { color: #336699; }
313 <p class="important">
314 Welcome on my awsome homepage.
318 The ``{% extends %}`` tag is the key here. It tells the template engine that
319 this template "extends" another template. When the template system evaluates
320 this template, first it locates the parent. The extends tag should be the
321 first tag in the template. Everything before it is printed out normally and
322 may cause confusion. For details about this behavior and how to take
323 advantage of it, see :ref:`null-master-fallback`.
325 The filename of the template depends on the template loader. For example the
326 :class:`FileSystemLoader` allows you to access other templates by giving the
327 filename. You can access templates in subdirectories with an slash::
329 {% extends "layout/default.html" %}
331 But this behavior can depend on the application embedding Jinja. Note that
332 since the child template doesn't define the ``footer`` block, the value from
333 the parent template is used instead.
335 You can't define multiple ``{% block %}`` tags with the same name in the
336 same template. This limitation exists because a block tag works in "both"
337 directions. That is, a block tag doesn't just provide a hole to fill - it
338 also defines the content that fills the hole in the *parent*. If there
339 were two similarly-named ``{% block %}`` tags in a template, that template's
340 parent wouldn't know which one of the blocks' content to use.
342 If you want to print a block multiple times you can however use the special
343 `self` variable and call the block with that name::
345 <title>{% block title %}{% endblock %}</title>
346 <h1>{{ self.title() }}</h1>
347 {% block body %}{% endblock %}
350 Unlike Python Jinja does not support multiple inheritance. So you can only have
351 one extends tag called per rendering.
357 It's possible to render the contents of the parent block by calling `super`.
358 This gives back the results of the parent block::
361 <h3>Table Of Contents</h3>
370 Jinja2 allows you to put the name of the block after the end tag for better
374 {% block inner_sidebar %}
376 {% endblock inner_sidebar %}
377 {% endblock sidebar %}
379 However the name after the `endblock` word must match the block name.
385 When generating HTML from templates, there's always a risk that a variable will
386 include characters that affect the resulting HTML. There are two approaches:
387 manually escaping each variable or automatically escaping everything by default.
389 Jinja supports both, but what is used depends on the application configuration.
390 The default configuaration is no automatic escaping for various reasons:
392 - escaping everything except of safe values will also mean that Jinja is
393 escaping variables known to not include HTML such as numbers which is
394 a huge performance hit.
396 - The information about the safety of a variable is very fragile. It could
397 happen that by coercing safe and unsafe values the return value is double
400 Working with Manual Escaping
401 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
403 If manual escaping is enabled it's **your** responsibility to escape
404 variables if needed. What to escape? If you have a variable that *may*
405 include any of the following chars (``>``, ``<``, ``&``, or ``"``) you
406 **have to** escape it unless the variable contains well-formed and trusted
407 HTML. Escaping works by piping the variable through the ``|e`` filter:
408 ``{{ user.username|e }}``.
410 Working with Automatic Escaping
411 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
413 When automatic escaping is enabled everything is escaped by default except
414 for values explicitly marked as safe. Those can either be marked by the
415 application or in the template by using the `|safe` filter. The main
416 problem with this approach is that Python itself doesn't have the concept
417 of tainted values so the information if a value is safe or unsafe can get
418 lost. If the information is lost escaping will take place which means that
419 you could end up with double escaped contents.
421 Double escaping is easy to avoid however, just rely on the tools Jinja2
422 provides and don't use builtin Python constructs such as the string modulo
425 Functions returning template data (macros, `super`, `self.BLOCKNAME`) return
428 String literals in templates with automatic escaping are considered unsafe
429 too. The reason for this is that the safe string is an extension to Python
430 and not every library will work properly with it.
433 List of Control Structures
434 --------------------------
436 A control structure refers to all those things that control the flow of a
437 program - conditionals (i.e. if/elif/else), for-loops, as well as things like
438 macros and blocks. Control structures appear inside ``{% ... %}`` blocks
439 in the default syntax.
444 Loop over each item in a sequence. For example, to display a list of users
445 provided in a variable called `users`::
449 {% for user in users %}
450 <li>{{ user.username|e }}</li>
454 Inside of a for loop block you can access some special variables:
456 +-----------------------+---------------------------------------------------+
457 | Variable | Description |
458 +=======================+===================================================+
459 | `loop.index` | The current iteration of the loop. (1 indexed) |
460 +-----------------------+---------------------------------------------------+
461 | `loop.index0` | The current iteration of the loop. (0 indexed) |
462 +-----------------------+---------------------------------------------------+
463 | `loop.revindex` | The number of iterations from the end of the loop |
465 +-----------------------+---------------------------------------------------+
466 | `loop.revindex0` | The number of iterations from the end of the loop |
468 +-----------------------+---------------------------------------------------+
469 | `loop.first` | True if first iteration. |
470 +-----------------------+---------------------------------------------------+
471 | `loop.last` | True if last iteration. |
472 +-----------------------+---------------------------------------------------+
473 | `loop.length` | The number of items in the sequence. |
474 +-----------------------+---------------------------------------------------+
475 | `loop.cycle` | A helper function to cycle between a list of |
476 | | sequences. See the explanation below. |
477 +-----------------------+---------------------------------------------------+
479 Within a for-loop, it's possible to cycle among a list of strings/variables
480 each time through the loop by using the special `loop.cycle` helper::
482 {% for row in rows %}
483 <li class="{{ loop.cycle('odd', 'even') }}">{{ row }}</li>
488 Unlike in Python it's not possible to `break` or `continue` in a loop. You
489 can however filter the sequence during iteration which allows you to skip
490 items. The following example skips all the users which are hidden::
492 {% for user in users if not user.hidden %}
493 <li>{{ user.username|e }}</li>
496 The advantage is that the special `loop` variable will count correctly thus
497 not counting the users not iterated over.
499 If no iteration took place because the sequence was empty or the filtering
500 removed all the items from the sequence you can render a replacement block
504 {% for user in users %}
505 <li>{{ user.username|e }}</li>
507 <li><em>no users found</em></li>
511 It is also possible to use loops recursively. This is useful if you are
512 dealing with recursive data such as sitemaps. To use loops recursively you
513 basically have to add the `recursive` modifier to the loop definition and
514 call the `loop` variable with the new iterable where you want to recurse.
516 The following example implements a sitemap with recursive loops::
519 {%- for item in sitemap recursive %}
520 <li><a href="{{ item.href|e }}">{{ item.title }}</a>
521 {%- if item.children -%}
522 <ul class="submenu">{{ loop(item.children) }}</ul>
531 The `if` statement in Jinja is comparable with the if statements of Python.
532 In the simplest form you can use it to test if a variable is defined, not
537 {% for user in users %}
538 <li>{{ user.username|e }}</li>
543 For multiple branches `elif` and `else` can be used like in Python. You can
544 use more complex :ref:`expressions` there too::
548 {% elif kenny.dead %}
549 You killed Kenny! You bastard!!!
551 Kenny looks okay --- so far
554 If can also be used as :ref:`inline expression <if-expression>` and for
555 :ref:`loop filtering <loop-filtering>`.
561 Macros are comparable with functions in regular programming languages. They
562 are useful to put often used idioms into reusable functions to not repeat
565 Here a small example of a macro that renders a form element::
567 {% macro input(name, value='', type='text', size=20) -%}
568 <input type="{{ type }}" name="{{ name }}" value="{{
569 value|e }}" size="{{ size }}">
572 The macro can then be called like a function in the namespace::
574 <p>{{ input('username') }}</p>
575 <p>{{ input('password', type='password') }}</p>
577 If the macro was defined in a different template you have to
578 :ref:`import <import>` it first.
580 Inside macros you have access to three special variables:
583 If more positional arguments are passed to the macro than accepted by the
584 macro they end up in the special `varargs` variable as list of values.
587 Like `varargs` but for keyword arguments. All unconsumed keyword
588 arguments are stored in this special variable.
591 If the macro was called from a :ref:`call<call>` tag the caller is stored
592 in this variable as macro which can be called.
594 Macros also expose some of their internal details. The following attributes
595 are available on a macro object:
598 The name of the macro. ``{{ input.name }}`` will print ``input``.
601 A tuple of the names of arguments the macro accepts.
604 A tuple of default values.
607 This is `true` if the macro accepts extra keyword arguments (ie: accesses
608 the special `kwargs` variable).
611 This is `true` if the macro accepts extra positional arguments (ie:
612 accesses the special `varargs` variable).
615 This is `true` if the macro accesses the special `caller` variable and may
616 be called from a :ref:`call<call>` tag.
624 In some cases it can be useful to pass a macro to another macro. For this
625 purpose you can use the special `call` block. The following example shows
626 a macro that takes advantage of the call functionality and how it can be
629 {% macro render_dialog(title, class='dialog') -%}
630 <div class="{{ class }}">
632 <div class="contents">
638 {% call render_dialog('Hello World') %}
639 This is a simple dialog rendered by using a macro and
643 It's also possible to pass arguments back to the call block. This makes it
644 useful as replacement for loops. Generally speaking a call block works
645 exactly like an macro, just that it doesn't have a name.
647 Here an example of how a call block can be used with arguments::
649 {% macro dump_users(users) -%}
651 {%- for user in users %}
652 <li><p>{{ user.username|e }}</p>{{ caller(user) }}</li>
657 {% call(user) dump_users(list_of_user) %}
660 <dd>{{ user.realname|e }}</dd>
662 <dd>{{ user.description }}</dd>
670 Filter sections allow you to apply regular Jinja2 filters on a block of
671 template data. Just wrap the code in the special `filter` section::
674 This text becomes uppercase
681 Inside code blocks you can also assign values to variables. Assignments at
682 top level (outside of blocks, macros or loops) are exported from the template
683 like top level macros and can be imported by other templates.
685 Assignments use the `set` tag and can have multiple targets::
687 {% set navigation = [('index.html', 'Index'), ('about.html', 'About')] %}
688 {% set key, value = call_something() %}
694 The `extends` tag can be used to extend a template from another one. You
695 can have multiple of them in a file but only one of them may be executed
696 at the time. There is no support for multiple inheritance. See the section
697 about :ref:`template-inheritance` above.
703 Blocks are used for inheritance and act as placeholders and replacements
704 at the same time. They are documented in detail as part of the section
705 about :ref:`template-inheritance`.
711 The `include` statement is useful to include a template and return the
712 rendered contents of that file into the current namespace::
714 {% include 'header.html' %}
716 {% include 'footer.html' %}
718 Included templates have access to the variables of the active context by
719 default. For more details about context behavior of imports and includes
720 see :ref:`import-visibility`.
727 Jinja2 supports putting often used code into macros. These macros can go into
728 different templates and get imported from there. This works similar to the
729 import statements in Python. It's important to know that imports are cached
730 and imported templates don't have access to the current template variables,
731 just the globals by defualt. For more details about context behavior of
732 imports and includes see :ref:`import-visibility`.
734 There are two ways to import templates. You can import the complete template
735 into a variable or request specific macros / exported variables from it.
737 Imagine we have a helper module that renders forms (called `forms.html`)::
739 {% macro input(name, value='', type='text') -%}
740 <input type="{{ type }}" value="{{ value|e }}" name="{{ name }}">
743 {%- macro textarea(name, value='', rows=10, cols=40) -%}
744 <textarea name="{{ name }}" rows="{{ rows }}" cols="{{ cols
745 }}">{{ value|e }}</textarea>
748 The easiest and most flexible is importing the whole module into a variable.
749 That way you can access the attributes::
751 {% import 'forms.html' as forms %}
754 <dd>{{ forms.input('username') }}</dd>
756 <dd>{{ forms.input('password', type='password') }}</dd>
758 <p>{{ forms.textarea('comment') }}</p>
761 Alternatively you can import names from the template into the current
764 {% from 'forms.html' import input as input_field, textarea %}
767 <dd>{{ input_field('username') }}</dd>
769 <dd>{{ input_field('password', type='password') }}</dd>
771 <p>{{ textarea('comment') }}</p>
773 Macros and variables starting with one ore more underscores are private and
777 .. _import-visibility:
779 Import Context Behavior
780 -----------------------
782 Per default included templates are passed the current context and imported
783 templates not. The reason for this is that imports unlike includes are
784 cached as imports are often used just as a module that holds macros.
786 This however can be changed of course explicitly. By adding `with context`
787 or `without context` to the import/include directive the current context
788 can be passed to the template and caching is disabled automatically.
792 {% from 'forms.html' import input with context %}
793 {% include 'header.html' without context %}
801 Jinja allows basic expressions everywhere. These work very similar to regular
802 Python and even if you're not working with Python you should feel comfortable
808 The simplest form of expressions are literals. Literals are representations
809 for Python objects such as strings and numbers. The following literals exist:
812 Everything between two double or single quotes is a string. They are
813 useful whenever you need a string in the template (for example as
814 arguments to function calls, filters or just to extend or include a
818 Integers and floating point numbers are created by just writing the
819 number down. If a dot is present the number is a float, otherwise an
820 integer. Keep in mind that for Python ``42`` and ``42.0`` is something
823 ['list', 'of', 'objects']:
824 Everything between two brackets is a list. Lists are useful to store
825 sequential data in or to iterate over them. For example you can easily
826 create a list of links using lists and tuples with a for loop::
829 {% for href, caption in [('index.html', 'Index'), ('about.html', 'About'),
830 ('downloads.html', 'Downloads')] %}
831 <li><a href="{{ href }}">{{ caption }}</a></li>
835 ('tuple', 'of', 'values'):
836 Tuples are like lists, just that you can't modify them. If the tuple
837 only has one item you have to end it with a comma. Tuples are usually
838 used to represent items of two or more elements. See the example above
841 {'dict': 'of', 'key': 'and', 'value': 'pairs'}:
842 A dict in Python is a structure that combines keys and values. Keys must
843 be unique and always have exactly one value. Dicts are rarely used in
844 templates, they are useful in some rare cases such as the :func:`xmlattr`
848 true is always true and false is always false.
852 The special constants `true`, `false` and `none` are indeed lowercase.
853 Because that caused confusion in the past, when writing `True` expands
854 to an undefined variable that is considered false, all three of them can
855 be written in title case too (`True`, `False`, and `None`). However for
856 consistency (all Jinja identifiers are lowercase) you should use the
862 Jinja allows you to calculate with values. This is rarely useful in templates
863 but exists for completeness sake. The following operators are supported:
866 Adds two objects with each other. Usually numbers but if both objects are
867 strings or lists you can concatenate them this way. This however is not
868 the preferred way to concatenate strings! For string concatenation have
869 a look at the ``~`` operator. ``{{ 1 + 1 }}`` is ``2``.
872 Substract two numbers from each other. ``{{ 3 - 2 }}`` is ``1``.
875 Divide two numbers. The return value will be a floating point number.
876 ``{{ 1 / 2 }}`` is ``{{ 0.5 }}``.
879 Divide two numbers and return the truncated integer result.
880 ``{{ 20 / 7 }}`` is ``2``.
883 Calculate the remainder of an integer division between the left and right
884 operand. ``{{ 11 % 7 }}`` is ``4``.
887 Multiply the left operand with the right one. ``{{ 2 * 2 }}`` would
888 return ``4``. This can also be used to repeat string multiple times.
889 ``{{ '=' * 80 }}`` would print a bar of 80 equal signs.
892 Raise the left operand to the power of the right operand. ``{{ 2**3 }}``
898 For `if` statements / `for` filtering or `if` expressions it can be useful to
899 combine group multiple expressions:
902 Return true if the left and the right operand is true.
905 Return true if the left or the right operand is true.
908 negate a statement (see below).
915 The ``is`` and ``in`` operators support negation using an infix notation
916 too: ``foo is not bar`` and ``foo not in bar`` instead of ``not foo is bar``
917 and ``not foo in bar``. All other expressions require a prefix notation:
918 ``not (foo and bar).``
924 The following operators are very useful but don't fit into any of the other
928 Perform sequence / mapping containment test. Returns true if the left
929 operand is contained in the right. ``{{ 1 in [1, 2, 3] }}`` would for
933 Performs a :ref:`test <tests>`.
936 Applies a :ref:`filter <filters>`.
939 Converts all operands into strings and concatenates them.
940 ``{{ "Hello " ~ name ~ "!" }}`` would return (assuming `name` is
941 ``'John'``) ``Hello John!``.
944 Call a callable: ``{{ post.render() }}``. Inside of the parentheses you
945 can use arguments and keyword arguments like in python:
946 ``{{ post.render(user, full=true) }}``.
949 Get an attribute of an object. (See :ref:`variables`)
957 It is also possible to use inline `if` expressions. These are useful in some
958 situations. For example you can use this to extend from one template if a
959 variable is defined, otherwise from the default layout template::
961 {% extends layout_template if layout_template is defined else 'master.html' %}
963 The general syntax is ``<do something> if <something is true> else <do
966 The `else` part is optional. If not provided the else block implicitly
967 evaluates into an undefined object::
969 {{ '[%s]' % page.title if page.title }}
974 List of Builtin Filters
975 -----------------------
982 List of Builtin Tests
983 ---------------------
988 List of Global Functions
989 ------------------------
991 The following functions are available in the global scope by default:
993 .. function:: range([start,] stop[, step])
995 Return a list containing an arithmetic progression of integers.
996 range(i, j) returns [i, i+1, i+2, ..., j-1]; start (!) defaults to 0.
997 When step is given, it specifies the increment (or decrement).
998 For example, range(4) returns [0, 1, 2, 3]. The end point is omitted!
999 These are exactly the valid indices for a list of 4 elements.
1001 This is useful to repeat a template block multiple times for example
1002 to fill a list. Imagine you have 7 users in the list but you want to
1003 render three empty items to enforce a height with CSS::
1006 {% for user in users %}
1007 <li>{{ user.username }}</li>
1009 {% for number in range(10 - users|count) %}
1010 <li class="empty"><span>...</span></li>
1014 .. function:: lipsum(n=5, html=True, min=20, max=100)
1016 Generates some lorem ipsum for the template. Per default five paragraphs
1017 with HTML are generated each paragraph between 20 and 100 words. If html
1018 is disabled regular text is returned. This is useful to generate simple
1019 contents for layout testing.
1021 .. function:: dict(\**items)
1023 A convenient alternative to dict literals. ``{'foo': 'bar'}`` is the same
1024 as ``dict(foo='bar')``.
1030 The following sections cover the built-in Jinja2 extensions that may be
1031 enabled by the application. The application could also provide further
1032 extensions not covered by this documentation. In that case there should
1033 be a separate document explaining the extensions.
1035 .. _i18n-in-templates:
1040 If the i18n extension is enabled it's possible to mark parts in the template
1041 as translatable. To mark a section as translatable you can use `trans`::
1043 <p>{% trans %}Hello {{ user }}!{% endtrans %}</p>
1045 To translate a template expression --- say, using template filters or just
1046 accessing an attribute of an object --- you need to bind the expression to a
1047 name for use within the translation block::
1049 <p>{% trans user=user.username %}Hello {{ user }}!{% endtrans %}</p>
1051 If you need to bind more than one expression inside a `trans` tag, separate
1052 the pieces with a comma (``,``)::
1054 {% trans book_title=book.title, author=author.name %}
1055 This is {{ book_title }} by {{ author }}
1058 Inside trans tags no statements are allowed, only variable tags are.
1060 To pluralize, specify both the singular and plural forms with the `pluralize`
1061 tag, which appears between `trans` and `endtrans`::
1063 {% trans count=list|length %}
1064 There is {{ count }} {{ name }} object.
1066 There are {{ count }} {{ name }} objects.
1069 Per default the first variable in a block is used to determine the correct
1070 singular or plural form. If that doesn't work out you can specify the name
1071 which should be used for pluralizing by adding it as parameter to `pluralize`::
1073 {% trans ..., user_count=users|length %}...
1074 {% pluralize user_count %}...{% endtrans %}
1076 It's also possible to translate strings in expressions. For that purpose
1077 three functions exist:
1079 _ `gettext`: translate a single string
1080 - `ngettext`: translate a pluralizable string
1081 - `_`: alias for `gettext`
1083 For example you can print a translated string easily this way::
1085 {{ _('Hello World!') }}
1087 To use placeholders you can use the `format` filter::
1089 {{ _('Hello %(user)s!')|format(user=user.username) }}
1091 {{ _('Hello %s')|format(user.username) }}
1093 For multiple placeholders always use keyword arguments to `format` as other
1094 languages may not use the words in the same order.
1097 Expression Statement
1098 ~~~~~~~~~~~~~~~~~~~~
1100 If the expression-statement extension is loaded a tag called `do` is available
1101 that works exactly like the regular variable expression (``{{ ... }}``) just
1102 that it doesn't print anything. This can be used to modify lists::
1104 {% do navigation.append('a string') %}
1110 If the application enables the :ref:`loopcontrols-extension` it's possible to
1111 use `break` and `continue` in loops. When `break` is reached, the loop is
1112 terminated, if `continue` is eached the processing is stopped and continues
1113 with the next iteration.
1115 Here a loop that skips every second item::
1117 {% for user in users %}
1118 {%- if loop.index is even %}{% continue %}{% endif %}
1122 Likewise a look that stops processing after the 10th iteration::
1124 {% for user in users %}
1125 {%- if loop.index >= 10 %}{% break %}{% endif %}
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