Being a web framework, Django needs a convenient way to generate HTML\ndynamically. The most common approach relies on templates. A template contains\nthe static parts of the desired HTML output as well as some special syntax\ndescribing how dynamic content will be inserted. For a hands-on example of\ncreating HTML pages with templates, see Tutorial 3.
\nA Django project can be configured with one or several template engines (or\neven zero if you don’t use templates). Django ships built-in backends for its\nown template system, creatively called the Django template language (DTL), and\nfor the popular alternative Jinja2. Backends for other template languages may\nbe available from third-parties.
\nDjango defines a standard API for loading and rendering templates regardless\nof the backend. Loading consists of finding the template for a given identifier\nand preprocessing it, usually compiling it to an in-memory representation.\nRendering means interpolating the template with context data and returning the\nresulting string.
\nThe Django template language is Django’s own\ntemplate system. Until Django 1.8 it was the only built-in option available.\nIt’s a good template library even though it’s fairly opinionated and sports a\nfew idiosyncrasies. If you don’t have a pressing reason to choose another\nbackend, you should use the DTL, especially if you’re writing a pluggable\napplication and you intend to distribute templates. Django’s contrib apps that\ninclude templates, like django.contrib.admin,\nuse the DTL.
\nFor historical reasons, both the generic support for template engines and the\nimplementation of the Django template language live in the django.template\nnamespace.
Templates engines are configured with the TEMPLATES setting. It’s a\nlist of configurations, one for each engine. The default value is empty. The\nsettings.py generated by the startproject command defines a\nmore useful value:
TEMPLATES = [\n {\n 'BACKEND': 'django.template.backends.django.DjangoTemplates',\n 'DIRS': [],\n 'APP_DIRS': True,\n 'OPTIONS': {\n # ... some options here ...\n },\n },\n]\nBACKEND is a dotted Python path to a template\nengine class implementing Django’s template backend API. The built-in backends\nare django.template.backends.django.DjangoTemplates and\ndjango.template.backends.jinja2.Jinja2.
Since most engines load templates from files, the top-level configuration for\neach engine contains two common settings:
\nDIRS defines a list of directories where the\nengine should look for template source files, in search order.
APP_DIRS tells whether the engine should\nlook for templates inside installed applications. Each backend defines a\nconventional name for the subdirectory inside applications where its\ntemplates should be stored.
While uncommon, it’s possible to configure several instances of the same\nbackend with different options. In that case you should define a unique\nNAME for each engine.
OPTIONS contains backend-specific settings.
The django.template.loader module defines two functions to load templates.
This function loads the template with the given name and returns a\nTemplate object.
The exact type of the return value depends on the backend that loaded the\ntemplate. Each backend has its own Template class.
get_template() tries each template engine in order until one succeeds.\nIf the template cannot be found, it raises\nTemplateDoesNotExist. If the template is found but\ncontains invalid syntax, it raises\nTemplateSyntaxError.
How templates are searched and loaded depends on each engine’s backend and\nconfiguration.
\nIf you want to restrict the search to a particular template engine, pass\nthe engine’s NAME in the using argument.
select_template() is just like get_template(), except it takes a\nlist of template names. It tries each name in order and returns the first\ntemplate that exists.
If loading a template fails, the following two exceptions, defined in\ndjango.template, may be raised:
This exception is raised when a template cannot be found.
\nThis exception is raised when a template was found but contains errors.
\nTemplate objects returned by get_template() and select_template()\nmust provide a render() method with the following signature:
Renders this template with a given context.
\nIf context is provided, it must be a dict. If it isn’t\nprovided, the engine will render the template with an empty context.
If request is provided, it must be an HttpRequest.\nThen the engine must make it, as well as the CSRF token, available in the\ntemplate. How this is achieved is up to each backend.
Here’s an example of the search algorithm. For this example the\nTEMPLATES setting is:
TEMPLATES = [\n {\n 'BACKEND': 'django.template.backends.django.DjangoTemplates',\n 'DIRS': [\n '/home/html/example.com',\n '/home/html/default',\n ],\n },\n {\n 'BACKEND': 'django.template.backends.jinja2.Jinja2',\n 'DIRS': [\n '/home/html/jinja2',\n ],\n },\n]\nIf you call get_template('story_detail.html'), here are the files Django\nwill look for, in order:
/home/html/example.com/story_detail.html ('django' engine)
/home/html/default/story_detail.html ('django' engine)
/home/html/jinja2/story_detail.html ('jinja2' engine)
If you call select_template(['story_253_detail.html', 'story_detail.html']),\nhere’s what Django will look for:
/home/html/example.com/story_253_detail.html ('django' engine)
/home/html/default/story_253_detail.html ('django' engine)
/home/html/jinja2/story_253_detail.html ('jinja2' engine)
/home/html/example.com/story_detail.html ('django' engine)
/home/html/default/story_detail.html ('django' engine)
/home/html/jinja2/story_detail.html ('jinja2' engine)
When Django finds a template that exists, it stops looking.
\n\nIt’s possible – and preferable – to organize templates in subdirectories\ninside each directory containing templates. The convention is to make a\nsubdirectory for each Django app, with subdirectories within those\nsubdirectories as needed.
\nDo this for your own sanity. Storing all templates in the root level of a\nsingle directory gets messy.
\nTo load a template that’s within a subdirectory, just use a slash, like so:
\nget_template('news/story_detail.html')\nUsing the same TEMPLATES option as above, this will attempt to load\nthe following templates:
/home/html/example.com/news/story_detail.html ('django' engine)
/home/html/default/news/story_detail.html ('django' engine)
/home/html/jinja2/news/story_detail.html ('jinja2' engine)
In addition, to cut down on the repetitive nature of loading and rendering\ntemplates, Django provides a shortcut function which automates the process.
\nrender_to_string() loads a template like get_template() and\ncalls its render() method immediately. It takes the following\narguments.
template_nameThe name of the template to load and render. If it’s a list of template\nnames, Django uses select_template() instead of\nget_template() to find the template.
contextA dict to be used as the template’s context for rendering.
context_instanceAn instance of Context or a subclass (e.g., an\ninstance of RequestContext) to use as the\ntemplate’s context.
requestAn optional HttpRequest that will be available\nduring the template’s rendering process.
See also the render() and\nrender_to_response() shortcuts, which call\nrender_to_string() and feed the result into an\nHttpResponse suitable for returning from a view.
Finally, you can use configured engines directly:
\nTemplate engines are available in django.template.engines:
from django.template import engines\n\ndjango_engine = engines['django']\ntemplate = django_engine.from_string("Hello {{ name }}!")\nThe lookup key — 'django' in this example — is the engine’s\nNAME.
Set BACKEND to\n'django.template.backends.django.DjangoTemplates' to configure a Django\ntemplate engine.
When APP_DIRS is True, DjangoTemplates\nengines look for templates in the templates subdirectory of installed\napplications. This generic name was kept for backwards-compatibility.
DjangoTemplates engines accept the following OPTIONS:
'allowed_include_roots': a list of strings representing allowed prefixes\nfor the {% ssi %} template tag. This is a security measure, so that\ntemplate authors can’t access files that they shouldn’t be accessing.
For example, if 'allowed_include_roots' is ['/home/html',\n'/var/www'], then {% ssi /home/html/foo.txt %} would work, but {%\nssi /etc/passwd %} wouldn’t.
It defaults to an empty list.
\n\n'context_processors': a list of dotted Python paths to callables that\nare used to populate the context when a template is rendered with a request.\nThese callables take a request object as their argument and return a\ndict of items to be merged into the context.
It defaults to an empty list.
\nSee RequestContext for more information.
'debug': a boolean that turns on/off template debug mode. If it is\nTrue, the fancy error page will display a detailed report for any\nexception raised during template rendering. This report contains the\nrelevant snippet of the template with the appropriate line highlighted.
It defaults to the value of the DEBUG setting.
'loaders': a list of dotted Python paths to template loader classes.\nEach Loader class knows how to import templates from a particular\nsource. Optionally, a tuple can be used instead of a string. The first item\nin the tuple should be the Loader class name, and subsequent items are\npassed to the Loader during initialization.
The default depends on the values of DIRS and\nAPP_DIRS.
See Loader types for details.
\n'string_if_invalid': the output, as a string, that the template system\nshould use for invalid (e.g. misspelled) variables.
It defaults to an empty string.
\nSee How invalid variables are handled for details.
\n'file_charset': the charset used to read template files on disk.
It defaults to the value of FILE_CHARSET.
Requires Jinja2 to be installed:
\n$ pip install Jinja2\nSet BACKEND to\n'django.template.backends.jinja2.Jinja2' to configure a Jinja2 engine.
When APP_DIRS is True, Jinja2 engines\nlook for templates in the jinja2 subdirectory of installed applications.
The most important entry in OPTIONS is\n'environment'. It’s a dotted Python path to a callable returning a Jinja2\nenvironment. It defaults to 'jinja2.Environment'. Django invokes that\ncallable and passes other options as keyword arguments. Furthermore, Django\nadds defaults that differ from Jinja2’s for a few options:
'autoescape': True
'auto_reload': settings.DEBUG
'undefined': DebugUndefined if settings.DEBUG else Undefined
The default configuration is purposefully kept to a minimum. The Jinja2\nbackend doesn’t create a Django-flavored environment. It doesn’t know about\nDjango context processors, filters, and tags. In order to use Django-specific\nAPIs, you must configure them into the environment.
For example, you can create myproject/jinja2.py with this content:
from __future__ import absolute_import # Python 2 only\n\nfrom django.contrib.staticfiles.storage import staticfiles_storage\nfrom django.core.urlresolvers import reverse\n\nfrom jinja2 import Environment\n\n\ndef environment(**options):\n env = Environment(**options)\n env.globals.update({\n 'static': staticfiles_storage.url,\n 'url': reverse,\n })\n return env\nand set the 'environment' option to 'myproject.jinja2.environment'.
Then you could use the following constructs in Jinja2 templates:
\n<img src="{{ static('path/to/company-logo.png') }}" alt="Company Logo">\n\n<a href="{{ url('admin:index') }}">Administration</a>\nThe concepts of tags and filters exist both in the Django template language\nand in Jinja2 but they’re used differently. Since Jinja2 supports passing\narguments to callables in templates, many features that require a template tag\nor filter in Django templates can be achieved simply by calling a function in\nJinja2 templates, as shown in the example above. Jinja2’s global namespace\nremoves the need for template context processors. The Django template language\ndoesn’t have an equivalent of Jinja2 tests.
\nHere’s how to implement a custom template backend in order to use another\ntemplate system. A template backend is a class that inherits\ndjango.template.backends.base.BaseEngine. It must implement\nget_template() and optionally from_string(). Here’s an example for a\nfictional foobar template library:
from django.template import TemplateDoesNotExist, TemplateSyntaxError\nfrom django.template.backends.base import BaseEngine\nfrom django.template.backends.utils import csrf_input_lazy, csrf_token_lazy\n\nimport foobar\n\n\nclass FooBar(BaseEngine):\n\n # Name of the subdirectory containing the templates for this engine\n # inside an installed application.\n app_dirname = 'foobar'\n\n def __init__(self, params):\n params = params.copy()\n options = params.pop('OPTIONS').copy()\n super(FooBar, self).__init__(params)\n\n self.engine = foobar.Engine(**options)\n\n\n def from_string(self, template_code):\n try:\n return Template(self.engine.from_string(template_code))\n except foobar.TemplateCompilationFailed as exc:\n raise TemplateSyntaxError(exc.args)\n\n def get_template(self, template_name):\n try:\n return Template(self.engine.get_template(template_name))\n except foobar.TemplateNotFound as exc:\n raise TemplateDoesNotExist(exc.args)\n except foobar.TemplateCompilationFailed as exc:\n raise TemplateSyntaxError(exc.args)\n\n\nclass Template(object):\n\n def __init__(self, template):\n self.template = template\n\n def render(self, context=None, request=None):\n if context is None:\n context = {}\n if request is not None:\n context['request'] = request\n context['csrf_input'] = csrf_input_lazy(request)\n context['csrf_token'] = csrf_token_lazy(request)\n return self.template.render(context)\nSee DEP 182 for more information.
\nA Django template is simply a text document or a Python string marked-up using\nthe Django template language. Some constructs are recognized and interpreted\nby the template engine. The main ones are variables and tags.
\nA template is rendered with a context. Rendering replaces variables with their\nvalues, which are looked up in the context, and executes tags. Everything else\nis output as is.
\nThe syntax of the Django template language involves four constructs.
\nA variable outputs a value from the context, which is a dict-like object\nmapping keys to values.
\nVariables are surrounded by {{ and }} like this:
My first name is {{ first_name }}. My last name is {{ last_name }}.\nWith a context of {'first_name': 'John', 'last_name': 'Doe'}, this\ntemplate renders to:
My first name is John. My last name is Doe.\nDictionary lookup, attribute lookup and list-index lookups are implemented\nwith a dot notation:
\n{{ my_dict.key }}\n{{ my_object.attribute }}\n{{ my_list.0 }}\nIf a variable resolves to a callable, the template system will call it with no\narguments and use its result instead of the callable.
\nFilters transform the values of variables and tag arguments.
\nThey look like this:
\n{{ django|title }}\nWith a context of {'django': 'the web framework for perfectionists with\ndeadlines'}, this template renders to:
The Web Framework For Perfectionists With Deadlines\nSome filters take an argument:
\n{{ my_date|date:"Y-m-d" }}\nA reference of built-in filters is\navailable as well as instructions for writing custom filters.
\nComments look like this:
\n{# this won't be rendered #}\nA {% comment %} tag provides multi-line comments.
django.template.Engine encapsulates an instance of the Django\ntemplate system. The main reason for instantiating an\nEngine directly is to use the Django template\nlanguage outside of a Django project.
django.template.backends.django.DjangoTemplates is a thin wrapper\nadapting django.template.Engine to Django’s template backend API.
django.template.Template represents a compiled template.\nTemplates are obtained with Engine.get_template() or Engine.from_string()
Likewise django.template.backends.django.Template is a thin wrapper\nadapting django.template.Template to the common template API.
django.template.Context holds some metadata in addition to the\ncontext data. It is passed to Template.render() for rendering a template.
django.template.RequestContext is a subclass of\nContext that stores the current\nHttpRequest and runs template context processors.
The common API doesn’t have an equivalent concept. Context data is passed in a\nplain dict and the current HttpRequest is passed\nseparately if needed.
Template loaders are responsible for locating templates, loading them, and\nreturning Template objects.
Django provides several built-in template loaders\nand supports custom template loaders.
\nContext processors are functions that receive the current\nHttpRequest as an argument and return a dict of\ndata to be added to the rendering context.
Their main use is to add common data shared by all templates to the context\nwithout repeating code in every view.
\nDjango provides many built-in context processors.\nImplementing a custom context processor is as simple as defining a function.
\n