Template Designer Documentation
===============================
+.. highlight:: html+jinja
+
This document describes the syntax and semantics of the template engine and
will be most useful as reference to those creating Jinja templates. As the
template engine is very flexible the configuration from the application might
the template. The template syntax is heavily inspired by Django and Python.
Below is a minimal template that illustrates a few basics. We will cover
-the details later in that document:
-
-.. sourcecode:: html+jinja
+the details later in that document::
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<html lang="en">
those.
You can use a dot (``.``) to access attributes of a variable, alternative the
-so-called "subscribe" syntax (``[]``) can be used. The following lines do
-the same:
-
-.. sourcecode:: jinja
+so-called "subscript" syntax (``[]``) can be used. The following lines do
+the same::
{{ foo.bar }}
{{ foo['bar'] }}
configuration, the default behavior is that it evaluates to an empty string
if printed and that you can iterate over it, but every other operation fails.
+.. _notes-on-subscriptions:
+
+.. admonition:: Implementation
+
+ For convenience sake ``foo.bar`` in Jinja2 does the following things on
+ the Python layer:
+
+ - check if there is an attribute called `bar` on `foo`.
+ - if there is not, check if there is an item ``'bar'`` in `foo`.
+ - if there is not, return an undefined object.
+
+ ``foo['bar']`` on the other hand works mostly the same with the a small
+ difference in the order:
+
+ - check if there is an item ``'bar'`` in `foo`.
+ - if there is not, check if there is an attribute called `bar` on `foo`.
+ - if there is not, return an undefined object.
+
+ This is important if an object has an item or attribute with the same
+ name. Additionally there is the :func:`attr` filter that just looks up
+ attributes.
+
.. _filters:
Filters
to test a variable against a common expression. To test a variable or
expression you add `is` plus the name of the test after the variable. For
example to find out if a variable is defined you can do ``name is defined``
-which will then return true or false depening on if `name` is defined.
+which will then return true or false depending on if `name` is defined.
Tests can accept arguments too. If the test only takes one argument you can
leave out the parentheses to group them. For example the following two
-expressions do the same:
-
-.. sourcecode:: jinja
+expressions do the same::
{% if loop.index is divisibleby 3 %}
{% if loop.index is divisibleby(3) %}
-The :ref:`builtin-tests` below descibes all the builtin tests.
+The :ref:`builtin-tests` below describes all the builtin tests.
Comments
To comment-out part of a line in a template, use the comment syntax which is
by default set to ``{# ... #}``. This is useful to comment out parts of the
template for debugging or to add information for other template designers or
-yourself:
-
-.. sourcecode:: jinja
+yourself::
{# note: disabled template because we no longer user this
{% for user in users %}
#}
+Whitespace Control
+------------------
+
+In the default configuration whitespace is not further modified by the
+template engine, so each whitespace (spaces, tabs, newlines etc.) is returned
+unchanged. If the application configures Jinja to `trim_blocks` the first
+newline after a a template tag is removed automatically (like in PHP).
+
+But you can also strip whitespace in templates by hand. If you put an minus
+sign (``-``) to the start or end of an block (for example a for tag), a
+comment or variable expression you can remove the whitespaces after or before
+that block::
+
+ {% for item in seq -%}
+ {{ item }}
+ {%- endfor %}
+
+This will yield all elements without whitespace between them. If `seq` was
+a list of numbers from ``1`` to ``9`` the output would be ``123456789``.
+
+If :ref:`line-statements` are enabled they strip leading whitespace
+automatically up to the beginning of the line.
+
+.. admonition:: Note
+
+ You must not use a whitespace between the tag and the minus sign.
+
+ **valid**::
+
+ {%- if foo -%}...{% endif %}
+
+ **invalid**::
+
+ {% - if foo - %}...{% endif %}
+
+
+Escaping
+--------
+
+It is sometimes desirable or even necessary to have Jinja ignore parts it
+would otherwise handle as variables or blocks. For example if the default
+syntax is used and you want to use ``{{`` as raw string in the template and
+not start a variable you have to use a trick.
+
+The easiest way is to output the variable delimiter (``{{``) by using a
+variable expression::
+
+ {{ '{{' }}
+
+For bigger sections it makes sense to mark a block `raw`. For example to
+put Jinja syntax as example into a template you can use this snippet::
+
+ {% raw %}
+ <ul>
+ {% for item in seq %}
+ <li>{{ item }}</li>
+ {% endfor %}
+ </ul>
+ {% endraw %}
+
+
+.. _line-statements:
+
+Line Statements
+---------------
+
+If line statements are enabled by the application it's possible to mark a
+line as a statement. For example if the line statement prefix is configured
+to ``#`` the following two examples are equivalent::
+
+ <ul>
+ # for item in seq
+ <li>{{ item }}</li>
+ # endfor
+ </ul>
+
+ <ul>
+ {% for item in seq %}
+ <li>{{ item }}</li>
+ {% endfor %}
+ </ul>
+
+The line statement prefix can appear anywhere on the line as long as no text
+precedes it. For better readability statements that start a block (such as
+`for`, `if`, `elif` etc.) may end with a colon::
+
+ # for item in seq:
+ ...
+ # endfor
+
+
+.. admonition:: Note
+
+ Line statements can span multiple lines if there are open parentheses,
+ braces or brackets::
+
+ <ul>
+ # for href, caption in [('index.html', 'Index'),
+ ('about.html', 'About')]:
+ <li><a href="{{ href }}">{{ caption }}</a></li>
+ # endfor
+ </ul>
+
+
+.. _template-inheritance:
+
Template Inheritance
--------------------
This template, which we'll call ``base.html``, defines a simple HTML skeleton
document that you might use for a simple two-column page. It's the job of
-"child" templates to fill the empty blocks with content:
-
-.. sourcecode:: html+jinja
+"child" templates to fill the empty blocks with content::
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<html lang="en">
Child Template
~~~~~~~~~~~~~~
-A child template might look like this:
-
-.. sourcecode:: html+jinja
+A child template might look like this::
{% extends "base.html" %}
{% block title %}Index{% endblock %}
this template "extends" another template. When the template system evaluates
this template, first it locates the parent. The extends tag should be the
first tag in the template. Everything before it is printed out normally and
-may cause confusion.
+may cause confusion. For details about this behavior and how to take
+advantage of it, see :ref:`null-master-fallback`.
The filename of the template depends on the template loader. For example the
:class:`FileSystemLoader` allows you to access other templates by giving the
-filename. You can access templates in subdirectories with an slash:
-
-.. sourcecode:: jinja
+filename. You can access templates in subdirectories with an slash::
{% extends "layout/default.html" %}
parent wouldn't know which one of the blocks' content to use.
If you want to print a block multiple times you can however use the special
-`self` variable and call the block with that name:
-
-.. sourcecode:: jinja
+`self` variable and call the block with that name::
<title>{% block title %}{% endblock %}</title>
<h1>{{ self.title() }}</h1>
{% block body %}{% endblock %}
-
Unlike Python Jinja does not support multiple inheritance. So you can only have
one extends tag called per rendering.
~~~~~~~~~~~~
It's possible to render the contents of the parent block by calling `super`.
-This gives back the results of the parent block:
-
-.. sourcecode:: jinja
+This gives back the results of the parent block::
{% block sidebar %}
<h3>Table Of Contents</h3>
{% endblock %}
+Named Block End-Tags
+~~~~~~~~~~~~~~~~~~~~
+
+Jinja2 allows you to put the name of the block after the end tag for better
+readability::
+
+ {% block sidebar %}
+ {% block inner_sidebar %}
+ ...
+ {% endblock inner_sidebar %}
+ {% endblock sidebar %}
+
+However the name after the `endblock` word must match the block name.
+
+
HTML Escaping
-------------
lost. If the information is lost escaping will take place which means that
you could end up with double escaped contents.
-Double escaping is easy to avoid however, just relay on the tools Jinja2
+Double escaping is easy to avoid however, just rely on the tools Jinja2
provides and don't use builtin Python constructs such as the string modulo
operator.
macros and blocks. Control structures appear inside ``{% ... %}`` blocks
in the default syntax.
-For Loops
-~~~~~~~~~
+For
+~~~
-Loop over each item in a sequece. For example, to display a list of users
-provided in a variable called `users`:
-
-.. sourcecode:: html+jinja
+Loop over each item in a sequence. For example, to display a list of users
+provided in a variable called `users`::
<h1>Members</h1>
<ul>
| | sequences. See the explanation below. |
+-----------------------+---------------------------------------------------+
-Within a for-loop, it's psosible to cycle among a list of strings/variables
-each time through the loop by using the special `loop.cycle` helper:
-
-.. sourcecode:: html+jinja
+Within a for-loop, it's possible to cycle among a list of strings/variables
+each time through the loop by using the special `loop.cycle` helper::
{% for row in rows %}
<li class="{{ loop.cycle('odd', 'even') }}">{{ row }}</li>
{% endfor %}
+With Jinja 2.1 an extra `cycle` helper exists that allows loop-unbound
+cycling. For more information have a look at the :ref:`builtin-globals`.
+
.. _loop-filtering:
Unlike in Python it's not possible to `break` or `continue` in a loop. You
can however filter the sequence during iteration which allows you to skip
-items. The following example skips all the users which are hidden:
-
-.. sourcecode:: html+jinja
+items. The following example skips all the users which are hidden::
{% for user in users if not user.hidden %}
<li>{{ user.username|e }}</li>
If no iteration took place because the sequence was empty or the filtering
removed all the items from the sequence you can render a replacement block
-by using `else`:
-
-.. sourcecode:: html+jinja
+by using `else`::
<ul>
{% for user in users %}
{% endif %}
</ul>
+It is also possible to use loops recursively. This is useful if you are
+dealing with recursive data such as sitemaps. To use loops recursively you
+basically have to add the `recursive` modifier to the loop definition and
+call the `loop` variable with the new iterable where you want to recurse.
+
+The following example implements a sitemap with recursive loops::
+
+ <ul class="sitemap">
+ {%- for item in sitemap recursive %}
+ <li><a href="{{ item.href|e }}">{{ item.title }}</a>
+ {%- if item.children -%}
+ <ul class="submenu">{{ loop(item.children) }}</ul>
+ {%- endif %}</li>
+ {%- endfor %}
+ </ul>
+
If
~~
The `if` statement in Jinja is comparable with the if statements of Python.
In the simplest form you can use it to test if a variable is defined, not
-empty or not false:
-
-.. sourcecode:: html+jinja
+empty or not false::
{% if users %}
<ul>
{% endif %}
For multiple branches `elif` and `else` can be used like in Python. You can
-use more complex :ref:`expressions` there too.
-
-.. sourcecode:: html+jinja
+use more complex :ref:`expressions` there too::
{% if kenny.sick %}
Kenny is sick.
:ref:`loop filtering <loop-filtering>`.
+Macros
+~~~~~~
+
+Macros are comparable with functions in regular programming languages. They
+are useful to put often used idioms into reusable functions to not repeat
+yourself.
+
+Here a small example of a macro that renders a form element::
+
+ {% macro input(name, value='', type='text', size=20) -%}
+ <input type="{{ type }}" name="{{ name }}" value="{{
+ value|e }}" size="{{ size }}">
+ {%- endmacro %}
+
+The macro can then be called like a function in the namespace::
+
+ <p>{{ input('username') }}</p>
+ <p>{{ input('password', type='password') }}</p>
+
+If the macro was defined in a different template you have to
+:ref:`import <import>` it first.
+
+Inside macros you have access to three special variables:
+
+`varargs`
+ If more positional arguments are passed to the macro than accepted by the
+ macro they end up in the special `varargs` variable as list of values.
+
+`kwargs`
+ Like `varargs` but for keyword arguments. All unconsumed keyword
+ arguments are stored in this special variable.
+
+`caller`
+ If the macro was called from a :ref:`call<call>` tag the caller is stored
+ in this variable as macro which can be called.
+
+Macros also expose some of their internal details. The following attributes
+are available on a macro object:
+
+`name`
+ The name of the macro. ``{{ input.name }}`` will print ``input``.
+
+`arguments`
+ A tuple of the names of arguments the macro accepts.
+
+`defaults`
+ A tuple of default values.
+
+`catch_kwargs`
+ This is `true` if the macro accepts extra keyword arguments (ie: accesses
+ the special `kwargs` variable).
+
+`catch_varargs`
+ This is `true` if the macro accepts extra positional arguments (ie:
+ accesses the special `varargs` variable).
+
+`caller`
+ This is `true` if the macro accesses the special `caller` variable and may
+ be called from a :ref:`call<call>` tag.
+
+If a macro name starts with an underscore it's not exported and can't
+be imported.
+
+
+.. _call:
+
+Call
+~~~~
+
+In some cases it can be useful to pass a macro to another macro. For this
+purpose you can use the special `call` block. The following example shows
+a macro that takes advantage of the call functionality and how it can be
+used::
+
+ {% macro render_dialog(title, class='dialog') -%}
+ <div class="{{ class }}">
+ <h2>{{ title }}</h2>
+ <div class="contents">
+ {{ caller() }}
+ </div>
+ </div>
+ {%- endmacro %}
+
+ {% call render_dialog('Hello World') %}
+ This is a simple dialog rendered by using a macro and
+ a call block.
+ {% endcall %}
+
+It's also possible to pass arguments back to the call block. This makes it
+useful as replacement for loops. Generally speaking a call block works
+exactly like an macro, just that it doesn't have a name.
+
+Here an example of how a call block can be used with arguments::
+
+ {% macro dump_users(users) -%}
+ <ul>
+ {%- for user in users %}
+ <li><p>{{ user.username|e }}</p>{{ caller(user) }}</li>
+ {%- endfor %}
+ </ul>
+ {%- endmacro %}
+
+ {% call(user) dump_users(list_of_user) %}
+ <dl>
+ <dl>Realname</dl>
+ <dd>{{ user.realname|e }}</dd>
+ <dl>Description</dl>
+ <dd>{{ user.description }}</dd>
+ </dl>
+ {% endcall %}
+
+
+Filters
+~~~~~~~
+
+Filter sections allow you to apply regular Jinja2 filters on a block of
+template data. Just wrap the code in the special `filter` section::
+
+ {% filter upper %}
+ This text becomes uppercase
+ {% endfilter %}
+
+
+Assignments
+~~~~~~~~~~~
+
+Inside code blocks you can also assign values to variables. Assignments at
+top level (outside of blocks, macros or loops) are exported from the template
+like top level macros and can be imported by other templates.
+
+Assignments use the `set` tag and can have multiple targets::
+
+ {% set navigation = [('index.html', 'Index'), ('about.html', 'About')] %}
+ {% set key, value = call_something() %}
+
+
+Extends
+~~~~~~~
+
+The `extends` tag can be used to extend a template from another one. You
+can have multiple of them in a file but only one of them may be executed
+at the time. There is no support for multiple inheritance. See the section
+about :ref:`template-inheritance` above.
+
+
+Block
+~~~~~
+
+Blocks are used for inheritance and act as placeholders and replacements
+at the same time. They are documented in detail as part of the section
+about :ref:`template-inheritance`.
+
+
+Include
+~~~~~~~
+
+The `include` statement is useful to include a template and return the
+rendered contents of that file into the current namespace::
+
+ {% include 'header.html' %}
+ Body
+ {% include 'footer.html' %}
+
+Included templates have access to the variables of the active context by
+default. For more details about context behavior of imports and includes
+see :ref:`import-visibility`.
+
+.. _import:
+
+Import
+~~~~~~
+
+Jinja2 supports putting often used code into macros. These macros can go into
+different templates and get imported from there. This works similar to the
+import statements in Python. It's important to know that imports are cached
+and imported templates don't have access to the current template variables,
+just the globals by defualt. For more details about context behavior of
+imports and includes see :ref:`import-visibility`.
+
+There are two ways to import templates. You can import the complete template
+into a variable or request specific macros / exported variables from it.
+
+Imagine we have a helper module that renders forms (called `forms.html`)::
+
+ {% macro input(name, value='', type='text') -%}
+ <input type="{{ type }}" value="{{ value|e }}" name="{{ name }}">
+ {%- endmacro %}
+
+ {%- macro textarea(name, value='', rows=10, cols=40) -%}
+ <textarea name="{{ name }}" rows="{{ rows }}" cols="{{ cols
+ }}">{{ value|e }}</textarea>
+ {%- endmacro %}
+
+The easiest and most flexible is importing the whole module into a variable.
+That way you can access the attributes::
+
+ {% import 'forms.html' as forms %}
+ <dl>
+ <dt>Username</dt>
+ <dd>{{ forms.input('username') }}</dd>
+ <dt>Password</dt>
+ <dd>{{ forms.input('password', type='password') }}</dd>
+ </dl>
+ <p>{{ forms.textarea('comment') }}</p>
+
+
+Alternatively you can import names from the template into the current
+namespace::
+
+ {% from 'forms.html' import input as input_field, textarea %}
+ <dl>
+ <dt>Username</dt>
+ <dd>{{ input_field('username') }}</dd>
+ <dt>Password</dt>
+ <dd>{{ input_field('password', type='password') }}</dd>
+ </dl>
+ <p>{{ textarea('comment') }}</p>
+
+Macros and variables starting with one ore more underscores are private and
+cannot be imported.
+
+
+.. _import-visibility:
+
+Import Context Behavior
+-----------------------
+
+Per default included templates are passed the current context and imported
+templates not. The reason for this is that imports unlike includes are
+cached as imports are often used just as a module that holds macros.
+
+This however can be changed of course explicitly. By adding `with context`
+or `without context` to the import/include directive the current context
+can be passed to the template and caching is disabled automatically.
+
+Here two examples::
+
+ {% from 'forms.html' import input with context %}
+ {% include 'header.html' without context %}
+
+.. admonition:: Note
+
+ In Jinja 2.0 the context that was passed to the included template
+ did not include variables define in the template. As a matter of
+ fact this did not work::
+
+ {% for box in boxes %}
+ {% include "render_box.html" %}
+ {% endfor %}
+
+ The included template ``render_box.html`` is not able to access
+ `box` in Jinja 2.0, but in Jinja 2.1.
+
+
.. _expressions:
Expressions
The simplest form of expressions are literals. Literals are representations
for Python objects such as strings and numbers. The following literals exist:
-``"Hello World"``
+"Hello World":
Everything between two double or single quotes is a string. They are
useful whenever you need a string in the template (for example as
arguments to function calls, filters or just to extend or include a
template).
-``42`` / ``42.23``
+42 / 42.23:
Integers and floating point numbers are created by just writing the
number down. If a dot is present the number is a float, otherwise an
integer. Keep in mind that for Python ``42`` and ``42.0`` is something
different.
-``['list', 'of', 'objects']``
+['list', 'of', 'objects']:
Everything between two brackets is a list. Lists are useful to store
sequential data in or to iterate over them. For example you can easily
- create a list of links using lists and tuples with a for loop.
-
- .. sourcecode:: html+jinja
+ create a list of links using lists and tuples with a for loop::
<ul>
{% for href, caption in [('index.html', 'Index'), ('about.html', 'About'),
{% endfor %}
</ul>
-``('tuple', 'of', 'values')``
+('tuple', 'of', 'values'):
Tuples are like lists, just that you can't modify them. If the tuple
only has one item you have to end it with a comma. Tuples are usually
used to represent items of two or more elements. See the example above
for more details.
-``{'dict': 'of', 'keys': 'and', 'value': 'pairs'}``
+{'dict': 'of', 'key': 'and', 'value': 'pairs'}:
A dict in Python is a structure that combines keys and values. Keys must
be unique and always have exactly one value. Dicts are rarely used in
templates, they are useful in some rare cases such as the :func:`xmlattr`
filter.
-``true`` and ``false``
- true is always true and false is always false. Keep in mind that those
- literals are lowercase!
+true / false:
+ true is always true and false is always false.
+
+.. admonition:: Note
+
+ The special constants `true`, `false` and `none` are indeed lowercase.
+ Because that caused confusion in the past, when writing `True` expands
+ to an undefined variable that is considered false, all three of them can
+ be written in title case too (`True`, `False`, and `None`). However for
+ consistency (all Jinja identifiers are lowercase) you should use the
+ lowercase versions.
Math
~~~~
Jinja allows you to calculate with values. This is rarely useful in templates
but exists for completeness sake. The following operators are supported:
-``+``
+\+
Adds two objects with each other. Usually numbers but if both objects are
strings or lists you can concatenate them this way. This however is not
the preferred way to concatenate strings! For string concatenation have
a look at the ``~`` operator. ``{{ 1 + 1 }}`` is ``2``.
-``-``
+\-
Substract two numbers from each other. ``{{ 3 - 2 }}`` is ``1``.
-``/``
+/
Divide two numbers. The return value will be a floating point number.
``{{ 1 / 2 }}`` is ``{{ 0.5 }}``.
-``//``
+//
Divide two numbers and return the truncated integer result.
``{{ 20 / 7 }}`` is ``2``.
-``%``
+%
Calculate the remainder of an integer division between the left and right
operand. ``{{ 11 % 7 }}`` is ``4``.
-``*``
+\*
Multiply the left operand with the right one. ``{{ 2 * 2 }}`` would
return ``4``. This can also be used to repeat string multiple times.
``{{ '=' * 80 }}`` would print a bar of 80 equal signs.
-``**``
+\**
Raise the left operand to the power of the right operand. ``{{ 2**3 }}``
would return ``8``.
For `if` statements / `for` filtering or `if` expressions it can be useful to
combine group multiple expressions:
-``and``
+and
Return true if the left and the right operand is true.
-``or``
+or
Return true if the left or the right operand is true.
-``not``
+not
negate a statement (see below).
-``()`` (group)
+(expr)
group an expression.
-Note that there is no support for any bit operations or something similar.
+.. admonition:: Note
-- special note regarding ``not``: The ``is`` and ``in`` operators support
- negation using an infix notation too: ``foo is not bar`` and
- ``foo not in bar`` instead of ``not foo is bar`` and ``not foo in bar``.
- All other expressions require a prefix notation: ``not (foo and bar).``
+ The ``is`` and ``in`` operators support negation using an infix notation
+ too: ``foo is not bar`` and ``foo not in bar`` instead of ``not foo is bar``
+ and ``not foo in bar``. All other expressions require a prefix notation:
+ ``not (foo and bar).``
Other Operators
The following operators are very useful but don't fit into any of the other
two categories:
-``in``
+in
Perform sequence / mapping containment test. Returns true if the left
operand is contained in the right. ``{{ 1 in [1, 2, 3] }}`` would for
example return true.
-``is``
- Performs a :ref:`tests <test>`.
+is
+ Performs a :ref:`test <tests>`.
-``|``
- Applies a :ref:`filters <filter>`.
+\|
+ Applies a :ref:`filter <filters>`.
-``~``
+~
Converts all operands into strings and concatenates them.
``{{ "Hello " ~ name ~ "!" }}`` would return (assuming `name` is
``'John'``) ``Hello John!``.
-``()`` (call)
+()
Call a callable: ``{{ post.render() }}``. Inside of the parentheses you
can use arguments and keyword arguments like in python:
``{{ post.render(user, full=true) }}``.
-``.`` / ``[]``
+. / []
Get an attribute of an object. (See :ref:`variables`)
If Expression
~~~~~~~~~~~~~
-blah
+It is also possible to use inline `if` expressions. These are useful in some
+situations. For example you can use this to extend from one template if a
+variable is defined, otherwise from the default layout template::
+
+ {% extends layout_template if layout_template is defined else 'master.html' %}
+
+The general syntax is ``<do something> if <something is true> else <do
+something else>``.
+
+The `else` part is optional. If not provided the else block implicitly
+evaluates into an undefined object::
+
+ {{ '[%s]' % page.title if page.title }}
.. _builtin-filters:
---------------------
.. jinjatests::
+
+.. _builtin-globals:
+
+List of Global Functions
+------------------------
+
+The following functions are available in the global scope by default:
+
+.. function:: range([start,] stop[, step])
+
+ Return a list containing an arithmetic progression of integers.
+ range(i, j) returns [i, i+1, i+2, ..., j-1]; start (!) defaults to 0.
+ When step is given, it specifies the increment (or decrement).
+ For example, range(4) returns [0, 1, 2, 3]. The end point is omitted!
+ These are exactly the valid indices for a list of 4 elements.
+
+ This is useful to repeat a template block multiple times for example
+ to fill a list. Imagine you have 7 users in the list but you want to
+ render three empty items to enforce a height with CSS::
+
+ <ul>
+ {% for user in users %}
+ <li>{{ user.username }}</li>
+ {% endfor %}
+ {% for number in range(10 - users|count) %}
+ <li class="empty"><span>...</span></li>
+ {% endfor %}
+ </ul>
+
+.. function:: lipsum(n=5, html=True, min=20, max=100)
+
+ Generates some lorem ipsum for the template. Per default five paragraphs
+ with HTML are generated each paragraph between 20 and 100 words. If html
+ is disabled regular text is returned. This is useful to generate simple
+ contents for layout testing.
+
+.. function:: dict(\**items)
+
+ A convenient alternative to dict literals. ``{'foo': 'bar'}`` is the same
+ as ``dict(foo='bar')``.
+
+.. class:: cycler(\*items)
+
+ The cycler allows you to cycle among values similar to how `loop.cycle`
+ works. Unlike `loop.cycle` however you can use this cycler outside of
+ loops or over multiple loops.
+
+ This is for example very useful if you want to show a list of folders and
+ files, with the folders on top, but both in the same list with alteranting
+ row colors.
+
+ The following example shows how `cycler` can be used::
+
+ {% set row_class = cycler('odd', 'even') %}
+ <ul class="browser">
+ {% for folder in folders %}
+ <li class="folder {{ row_class.next() }}">{{ folder|e }}</li>
+ {% endfor %}
+ {% for filename in files %}
+ <li class="file {{ row_class.next() }}">{{ filename|e }}</li>
+ {% endfor %}
+ </ul>
+
+ A cycler has the following attributes and methods:
+
+ .. method:: reset()
+
+ Resets the cycle to the first item.
+
+ .. method:: next()
+
+ Goes one item a head and returns the then current item.
+
+ .. attribute:: current
+
+ Returns the current item.
+
+ **new in Jinja 2.1**
+
+
+Extensions
+----------
+
+The following sections cover the built-in Jinja2 extensions that may be
+enabled by the application. The application could also provide further
+extensions not covered by this documentation. In that case there should
+be a separate document explaining the extensions.
+
+.. _i18n-in-templates:
+
+i18n
+~~~~
+
+If the i18n extension is enabled it's possible to mark parts in the template
+as translatable. To mark a section as translatable you can use `trans`::
+
+ <p>{% trans %}Hello {{ user }}!{% endtrans %}</p>
+
+To translate a template expression --- say, using template filters or just
+accessing an attribute of an object --- you need to bind the expression to a
+name for use within the translation block::
+
+ <p>{% trans user=user.username %}Hello {{ user }}!{% endtrans %}</p>
+
+If you need to bind more than one expression inside a `trans` tag, separate
+the pieces with a comma (``,``)::
+
+ {% trans book_title=book.title, author=author.name %}
+ This is {{ book_title }} by {{ author }}
+ {% endtrans %}
+
+Inside trans tags no statements are allowed, only variable tags are.
+
+To pluralize, specify both the singular and plural forms with the `pluralize`
+tag, which appears between `trans` and `endtrans`::
+
+ {% trans count=list|length %}
+ There is {{ count }} {{ name }} object.
+ {% pluralize %}
+ There are {{ count }} {{ name }} objects.
+ {% endtrans %}
+
+Per default the first variable in a block is used to determine the correct
+singular or plural form. If that doesn't work out you can specify the name
+which should be used for pluralizing by adding it as parameter to `pluralize`::
+
+ {% trans ..., user_count=users|length %}...
+ {% pluralize user_count %}...{% endtrans %}
+
+It's also possible to translate strings in expressions. For that purpose
+three functions exist:
+
+_ `gettext`: translate a single string
+- `ngettext`: translate a pluralizable string
+- `_`: alias for `gettext`
+
+For example you can print a translated string easily this way::
+
+ {{ _('Hello World!') }}
+
+To use placeholders you can use the `format` filter::
+
+ {{ _('Hello %(user)s!')|format(user=user.username) }}
+ or
+ {{ _('Hello %s')|format(user.username) }}
+
+For multiple placeholders always use keyword arguments to `format` as other
+languages may not use the words in the same order.
+
+
+Expression Statement
+~~~~~~~~~~~~~~~~~~~~
+
+If the expression-statement extension is loaded a tag called `do` is available
+that works exactly like the regular variable expression (``{{ ... }}``) just
+that it doesn't print anything. This can be used to modify lists::
+
+ {% do navigation.append('a string') %}
+
+
+Loop Controls
+~~~~~~~~~~~~~
+
+If the application enables the :ref:`loopcontrols-extension` it's possible to
+use `break` and `continue` in loops. When `break` is reached, the loop is
+terminated, if `continue` is eached the processing is stopped and continues
+with the next iteration.
+
+Here a loop that skips every second item::
+
+ {% for user in users %}
+ {%- if loop.index is even %}{% continue %}{% endif %}
+ ...
+ {% endfor %}
+
+Likewise a look that stops processing after the 10th iteration::
+
+ {% for user in users %}
+ {%- if loop.index >= 10 %}{% break %}{% endif %}
+ {%- endfor %}
projects / jinja2.git / blobdiff