Updated templates API reference.

====================================================

The Django template language: For Python programmers

The Django template language: for Python programmers

====================================================

.. currentmodule:: django.template

rendering. Start with the :ref:`introduction to the Django template language

<template-language-intro>` if you aren't familiar with these concepts.

If you're looking to use the Django template system as part of another

application -- i.e., without the rest of the framework -- make sure to read

the `configuration`_ section later in this document.

Overview

========

.. _configuration: `configuring the template system in standalone mode`_

Using the template system in Python is a three-step process:

Using the template system

=========================

1. You configure an :class:`Engine`.

2. You compile template code into a :class:`Template`.

3. You render the template with a :class:`Context`.

.. class:: Template

Django projects generally rely on the :ref:`high level, backend agnostic APIs

<template-engines>` for each of these steps instead of the template system's

lower level APIs:

Using the template system in Python is a two-step process:

1. For each :class:`~django.template.backends.django.DjangoTemplates` backend

   in the :setting:`TEMPLATES` setting, Django instantiates an

   :class:`Engine`. :class:`~django.template.backends.django.DjangoTemplates`

   wraps :class:`Engine` and adapts it to the common template backend API.

2. The :mod:`django.template.loader` module provides functions such as

   :func:`~django.template.loader.get_template` for loading templates. They

   return a ``django.template.backends.django.Template`` which wraps the

   actual :class:`django.template.Template`.

3. The ``Template`` obtained in the previous step has a

   :meth:`~django.template.backends.base.Template.render` method which

   marshals a context and possibly a request into a :class:`Context` and

   delegates the rendering to the underlying :class:`Template`.

* First, you compile the raw template code into a ``Template`` object.

* Then, you call the ``render()`` method of the ``Template`` object with a

  given context.

Configuring an engine

=====================

Compiling a string

------------------

.. class:: Engine([dirs][, app_dirs][, allowed_include_roots][, context_processors][, debug][, loaders][, string_if_invalid][, file_charset])

    .. versionadded:: 1.8

    When instantiating an ``Engine`` all arguments must be passed as keyword

    arguments:

    * ``dirs`` is a list of directories where the engine should look for

      template source files. It is used to configure

      :class:`filesystem.Loader <django.template.loaders.filesystem.Loader>`.

      It defaults to an empty list.

    * ``app_dirs`` only affects the default value of ``loaders``. See below.

      It defaults to ``False``.

    * ``allowed_include_roots`` is a list of strings representing allowed

      prefixes for the ``{% ssi %}`` template tag. This is a security measure,

      so that template authors can't access files that they shouldn't be

      accessing.

      For example, if ``'allowed_include_roots'`` is ``['/home/html',

      '/var/www']``, then ``{% ssi /home/html/foo.txt %}`` would work, but ``{%

      ssi /etc/passwd %}`` wouldn't.

      It defaults to an empty list.

      .. deprecated:: 1.8

          ``allowed_include_roots`` is deprecated.

    * ``context_processors`` is a list of dotted Python paths to callables

      that are used to populate the context when a template is rendered with a

      request. These callables take a request object as their argument and

      return a :class:`dict` of items to be merged into the context.

      It defaults to an empty list.

      See :class:`~django.template.RequestContext` for more information.

    * ``debug`` is a boolean that turns on/off template debug mode. If it is

      ``True``, the template engine will store additional debug information

      which can be used to display a detailed report for any exception raised

      during template rendering.

      It defaults to ``False``.

    * ``loaders`` is a list of template loader classes, specified as strings.

      Each ``Loader`` class knows how to import templates from a particular

      source. Optionally, a tuple can be used instead of a string. The first

      item in the tuple should be the ``Loader`` class name, subsequent items

      are passed to the ``Loader`` during initialization.

      It defaults to a list containing:

      * ``'django.template.loaders.filesystem.Loader'``

      * ``'django.template.loaders.app_directories.Loader'`` if and only if

        ``app_dirs`` is ``True``.

      See :ref:`template-loaders` for details.

    * ``string_if_invalid`` is the output, as a string, that the template

      system should use for invalid (e.g. misspelled) variables.

      It defaults to the empty string.

      See :ref:`invalid-template-variables` for details.

    * ``file_charset`` is the charset used to read template files on disk.

      It defaults to ``'utf-8'``.

.. staticmethod:: Engine.get_default()

    When a Django project configures one and only one

    :class:`~django.template.backends.django.DjangoTemplates` engine, this

    method returns the underlying :class:`Engine`. In other circumstances it

    will raise :exc:`~django.core.exceptions.ImproperlyConfigured`.

    It's required for preserving APIs that rely on a globally available,

    implicitly configured engine. Any other use is strongly discouraged.

.. method:: Engine.from_string(template_code)

    Compiles the given template code and returns a :class:`Template` object.

.. method:: Engine.get_template(template_name)

    Loads a template with the given name, compiles it and returns a

    :class:`Template` object.

The easiest way to create a ``Template`` object is by instantiating it

directly. The class lives at :class:`django.template.Template`. The constructor

takes one argument -- the raw template code::

.. method:: Engine.select_template(self, template_name_list)

    >>> from django.template import Template

    >>> t = Template("My name is {{ my_name }}.")

    >>> print(t)

    <django.template.Template instance>

    Like :meth:`~Engine.get_template`, except it takes a list of names

    and returns the first template that was found.

Loading a template

==================

The recommended way to create a :class:`Template` is by calling the factory

methods of the :class:`Engine`: :meth:`~Engine.get_template`,

:meth:`~Engine.select_template` and :meth:`~Engine.from_string`.

In a Django project where the :setting:`TEMPLATES` setting defines exactly one

:class:`~django.template.backends.django.DjangoTemplates` engine, it's

possible to instantiate a :class:`Template` directly.

.. class:: Template

    This class lives at ``django.template.Template``. The constructor takes

    one argument — the raw template code::

        from django.template import Template

        template = Template("My name is {{ my_name }}.")

.. admonition:: Behind the scenes

    The system only parses your raw template code once -- when you create the

    ``Template`` object. From then on, it's stored internally as a "node"

    ``Template`` object. From then on, it's stored internally as a tree

    structure for performance.

    Even the parsing itself is quite fast. Most of the parsing happens via a

    single call to a single, short, regular expression.

Rendering a context

-------------------

===================

.. method:: Template.render(context)

Once you have a compiled :class:`Template` object, you can render a context

with it. You can reuse the same template to render it several times with

different contexts.

Once you have a compiled ``Template`` object, you can render a context -- or

multiple contexts -- with it. The ``Context`` class lives at

:class:`django.template.Context`, and the constructor takes two (optional)

arguments:

.. class:: Context([dict_][, current_app])

    This class lives at ``django.template.Context``. The constructor takes

    two optional arguments:

    * A dictionary mapping variable names to variable values.

      to help :ref:`resolve namespaced URLs<topics-http-reversing-url-namespaces>`.

      If you're not using namespaced URLs, you can ignore this argument.

Call the ``Template`` object's ``render()`` method with the context to "fill" the

template::

      .. deprecated:: 1.8

          The ``curent_app`` argument is deprecated. If you need it, you must

          now use a :class:`RequestContext` instead of a :class:`Context`.

    For details, see :ref:`playing-with-context` below.

.. method:: Template.render(context)

    Call the :class:`Template` object's ``render()`` method with a

    :class:`Context` to "fill" the template::

        >>> from django.template import Context, Template

    >>> t = Template("My name is {{ my_name }}.")

        >>> template = Template("My name is {{ my_name }}.")

    >>> c = Context({"my_name": "Adrian"})

    >>> t.render(c)

        >>> context = Context({"my_name": "Adrian"})

        >>> template.render(context)

        "My name is Adrian."

    >>> c = Context({"my_name": "Dolores"})

    >>> t.render(c)

        >>> context = Context({"my_name": "Dolores"})

        >>> template.render(context)

        "My name is Dolores."

Variables and lookups

~~~~~~~~~~~~~~~~~~~~~

---------------------

Variable names must consist of any letter (A-Z), any digit (0-9), an underscore

(but they must not start with an underscore) or a dot.

  propagated, unless the exception has an attribute

  ``silent_variable_failure`` whose value is ``True``. If the exception

  *does* have a ``silent_variable_failure`` attribute whose value is

  ``True``, the variable will render as the value of the

  ``True``, the variable will render as the value of the engine's

  ``string_if_invalid`` configuration option (an empty string, by default).

  Example::

  silently.

* A variable can only be called if it has no required arguments. Otherwise,

  the system will return the value of the ``string_if_invalid`` option.

  the system will return the value of the engine's ``string_if_invalid``

  option.

.. _alters-data-description:

.. _invalid-template-variables:

How invalid variables are handled

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

---------------------------------

Generally, if a variable doesn't exist, the template system inserts the

value of the ``string_if_invalid`` configuration option, which is set to

Generally, if a variable doesn't exist, the template system inserts the value

of the engine's ``string_if_invalid`` configuration option, which is set to

``''`` (the empty string) by default.

Filters that are applied to an invalid variable will only be applied if

    Generally, ``string_if_invalid`` should only be enabled in order to debug

    a specific template problem, then cleared once debugging is complete.

Builtin variables

~~~~~~~~~~~~~~~~~

Built-in variables

------------------

Every context contains ``True``, ``False`` and ``None``. As you would expect,

these variables resolve to the corresponding Python objects.

Limitations with string literals

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

--------------------------------

Django's template language has no way to escape the characters used for its own

syntax. For example, the :ttag:`templatetag` tag is required if you need to

If you need to use strings with these sequences, store them in template

variables or use a custom template tag or filter to workaround the limitation.

Playing with Context objects

----------------------------

.. _playing-with-context:

.. class:: Context

Playing with Context objects

============================

Most of the time, you'll instantiate ``Context`` objects by passing in a

Most of the time, you'll instantiate :class:`Context` objects by passing in a

fully-populated dictionary to ``Context()``. But you can add and delete items

from a ``Context`` object once it's been instantiated, too, using standard

dictionary syntax::

    >>> c['foo']

    'first level'

Using a ``Context`` as a stack comes in handy in some custom template tags, as

you'll see below.

Using a ``Context`` as a stack comes in handy in :ref:`some custom template

tags <howto-writing-custom-template-tags>`.

.. method:: Context.flatten()

            c1 = Context()

            c1['update'] = 'value'

            self.assertEqual(c1.flatten(), {

                'True': True, 'None': None, 'False': False,

                'update': 'value'})

                'True': True,

                'None': None,

                'False': False,

                'update': 'value',

            })

.. _subclassing-context-requestcontext:

Subclassing Context: RequestContext

-----------------------------------

.. class:: RequestContext

.. class:: RequestContext(request[, dict_][, processors])

Django comes with a special ``Context`` class,

``django.template.RequestContext``, that acts slightly differently than the

``django.template.RequestContext``, that acts slightly differently from the

normal ``django.template.Context``. The first difference is that it takes an

:class:`~django.http.HttpRequest` as its first argument. For example::

    })

The second difference is that it automatically populates the context with a

few variables, according to the ``'context_processors'`` option in the

:setting:`TEMPLATES` setting.

few variables, according to the engine's ``context_processors`` configuration

option.

The ``'context_processors'`` option is a list of callables -- called **context

The ``context_processors`` option is a list of callables -- called **context

processors** -- that take a request object as their argument and return a

dictionary of items to be merged into the context. In the default generated

settings file, the default template engine contains the following context

    ``django.core.context_processors`` to

    ``django.template.context_processors`` in Django 1.8.

In addition to these, ``RequestContext`` always uses

``django.template.context_processors.csrf``.  This is a security

related context processor required by the admin and other contrib apps, and,

in case of accidental misconfiguration, it is deliberately hardcoded in and

cannot be turned off in the ``'context_processors'`` option.

In addition to these, :class:`RequestContext` always enables

``'django.template.context_processors.csrf'``.  This is a security related

context processor required by the admin and other contrib apps, and, in case

of accidental misconfiguration, it is deliberately hardcoded in and cannot be

turned off in the ``context_processors`` option.

Each processor is applied in order. That means, if one processor adds a

variable to the context and a second processor adds a variable with the same

.. admonition:: When context processors are applied

    Context processors are applied *after* the context itself is processed.

    This means that a context processor may overwrite variables you've

    supplied to your ``Context`` or ``RequestContext``, so take care

    to avoid variable names that overlap with those supplied by your

    context processors.

    Context processors are applied on top of context data. This means that a

    context processor may overwrite variables you've supplied to your

    :class:`Context` or :class:`RequestContext`, so take care to avoid

    variable names that overlap with those supplied by your context

    processors.

    If you want context data to take priority over context processors, use the

    following pattern::

        from django.template import RequestContext

        request_context = RequestContext(request)

        request_context.push({"my_name": "Adrian"})

Also, you can give ``RequestContext`` a list of additional processors, using the

optional, third positional argument, ``processors``. In this example, the

``RequestContext`` instance gets a ``ip_address`` variable::

    Django does this to allow context data to override context processors in

    APIs such as :func:`~django.shortcuts.render` and

    :class:`~django.template.response.TemplateResponse`.

Also, you can give :class:`RequestContext` a list of additional processors,

using the optional, third positional argument, ``processors``. In this

example, the :class:`RequestContext` instance gets a ``ip_address`` variable::

    from django.http import HttpResponse

    from django.template import RequestContext

        }, [ip_address_processor])

        return HttpResponse(t.render(c))

.. note::

    If you're using Django's :func:`~django.shortcuts.render_to_response()`

    shortcut to populate a template with the contents of a dictionary, your

    template will be passed a ``Context`` instance by default (not a

    ``RequestContext``). To use a ``RequestContext`` in your template

    rendering, use the :meth:`~django.shortcuts.render()` shortcut which is

    the same as a call to :func:`~django.shortcuts.render_to_response()` with a

    ``context_instance`` argument that forces the use of a ``RequestContext``.

Built-in template context processors

------------------------------------

.. _context-processors:

       The ``DEFAULT_MESSAGE_LEVELS`` variable was added.

Writing your own context processors

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

-----------------------------------

A context processor has a very simple interface: It's just a Python function

that takes one argument, an :class:`~django.http.HttpRequest` object, and

Custom context processors can live anywhere in your code base. All Django

cares about is that your custom context processors are pointed to by the

``'context_processors'`` option in your :setting:`TEMPLATES` setting.

``'context_processors'`` option in your :setting:`TEMPLATES` setting — or the

``context_processors`` argument of :class:`~django.template.Engine` if you're

using it directly.

Loading templates

-----------------

=================

Generally, you'll store templates in files on your filesystem rather than using

the low-level ``Template`` API yourself. Save templates in a directory

specified as a **template directory**.

Generally, you'll store templates in files on your filesystem rather than

using the low-level :class:`~django.template.Template` API yourself. Save

templates in a directory specified as a **template directory**.

Django searches for template directories in a number of places, depending on

your template-loader settings (see "Loader types" below), but the most basic

your template loading settings (see "Loader types" below), but the most basic

way of specifying template directories is by using the :setting:`DIRS

<TEMPLATES-DIRS>` option.

The DIRS option

~~~~~~~~~~~~~~~

The :setting:`DIRS <TEMPLATES-DIRS>` option

-------------------------------------------

.. versionchanged:: 1.8

Tell Django what your template directories are by using the :setting:`DIRS

<TEMPLATES-DIRS>` option in the :setting:`TEMPLATES` setting in your settings

file. This should be set to a list of strings that contain full paths to your

template directory(ies). Example::

file — or the ``dirs`` argument of :class:`~django.template.Engine`. This

should be set to a list of strings that contain full paths to your template

directories::

    TEMPLATES = [

        {

.. _template-loaders:

Loader types

~~~~~~~~~~~~

------------

By default, Django uses a filesystem-based template loader, but Django comes

with a few other template loaders, which know how to load templates from other

Some of these other loaders are disabled by default, but you can activate them

by adding a ``'loaders'`` option to your ``DjangoTemplates`` backend in the

:setting:`TEMPLATES` setting. ``'loaders'`` should be a list of strings or

:setting:`TEMPLATES` setting or passing a ``loaders`` argument to

:class:`~django.template.Engine`. ``loaders`` should be a list of strings or

tuples, where each represents a template loader class. Here are the template

loaders that come with Django:

    it caches a list of which :setting:`INSTALLED_APPS` packages have a

    ``templates`` subdirectory.

    This loader is enabled if and only if :setting:`APP_DIRS

    <TEMPLATES-APP_DIRS>` is set::

    You can enable this loader simply by setting

    :setting:`APP_DIRS <TEMPLATES-APP_DIRS>` to ``True``::

        TEMPLATES = [{

            'BACKEND': 'django.template.backends.django.DjangoTemplates',

            'APP_DIRS': True,

        }]

``django.template.loaders.eggs.Loader``

.. class:: eggs.Loader

            'DIRS': [os.path.join(BASE_DIR, 'templates')],

            'OPTIONS': {

                'loaders': [

                    ('django.template.loaders.cached.Loader', (

                    ('django.template.loaders.cached.Loader', [

                        'django.template.loaders.filesystem.Loader',

                        'django.template.loaders.app_directories.Loader',

                    )),

                    ]),

                ],

            },

        }]

        cached loader, but if you're using custom template tags that come from

        third party packages, or that you wrote yourself, you should ensure

        that the ``Node`` implementation for each tag is thread-safe. For more

        information, see :ref:`template tag thread safety

        considerations<template_tag_thread_safety>`.

        information, see :ref:`template tag thread safety considerations

        <template_tag_thread_safety>`.

    This loader is disabled by default.

.. _custom-template-loaders:

Custom loaders

~~~~~~~~~~~~~~

--------------

Custom ``Loader`` classes should inherit from

``django.template.loaders.base.Loader`` and override the

.. currentmodule:: django.template

Template origin

~~~~~~~~~~~~~~~

===============

.. versionadded:: 1.7

When :setting:`TEMPLATE_DEBUG` is ``True`` template objects will have an

``origin`` attribute depending on the source they are loaded from.

When an :class:`~django.template.Engine` is initialized with ``debug=True``,

its templates have an ``origin`` attribute depending on the source they are

loaded from. For engines initialized by Django, ``debug`` defaults to the

value of :setting:`TEMPLATE_DEBUG`.

.. class:: loader.LoaderOrigin

    .. attribute:: source

        The string used to create the template.

Configuring the template system in standalone mode

==================================================

.. note::

    This section is only of interest to people trying to use the template

    system as an output component in another application. If you're using the

    template system as part of a Django application, nothing here applies to

    you.

Normally, Django will load all the configuration information it needs from its

own default configuration file, combined with the settings in the module given

in the :envvar:`DJANGO_SETTINGS_MODULE` environment variable. But if you're

using the template system independently of the rest of Django, the environment

variable approach isn't very convenient, because you probably want to configure

the template system in line with the rest of your application rather than

dealing with settings files and pointing to them via environment variables.

To solve this problem, you need to use the manual configuration option described

in :ref:`settings-without-django-settings-module`. Simply import the appropriate

pieces of the templating system and then, *before* you call any of the

templating functions, call :func:`django.conf.settings.configure()` with any

settings you wish to specify. You might want to consider setting at least

:setting:`DIRS <TEMPLATES-DIRS>` (if you're going to use template loaders),

:setting:`DEFAULT_CHARSET` (although the default of ``utf-8`` is probably fine)

and :setting:`TEMPLATE_DEBUG`. If you plan to use the :ttag:`url` template tag,

you will also need to set the :setting:`ROOT_URLCONF` setting. All available

settings are described in the :doc:`settings documentation </ref/settings>`,

and any setting starting with ``TEMPLATE_`` is of obvious interest.