Engine(
libraries={
"myapp_tags": "path.to.myapp.tags",
"admin.urls": "django.contrib.admin.templatetags.admin_urls",
Libraries can be loaded by passing the corresponding dictionary key to
the {% load %} tag.
'builtins': A list of dotted Python paths of template tag modules to
add to built-ins. For example:
Engine(
builtins=["myapp.builtins"],
Tags and filters from built-in libraries can be used without first calling
the {% load %} tag.
static Engine.get_default()[source]
Returns the underlying Engine from the first configured
DjangoTemplates engine. Raises
ImproperlyConfigured if no engines are
configured.
It’s required for preserving APIs that rely on a globally available,
implicitly configured engine. Any other use is strongly discouraged.
Engine.get_template(template_name)[source]
Loads a template with the given name, compiles it and returns a
Template object.
Engine.select_template(template_name_list)[source]
Like 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 Template is by calling the factory
methods of the Engine: get_template(),
select_template() and from_string().
In a Django project where the TEMPLATES setting defines a
DjangoTemplates engine, it’s
possible to instantiate a Template directly. If more than one
DjangoTemplates engine is defined,
the first one will be used.
class Template[source]
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 }}.")
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 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
Once you have a compiled Template object, you can render a context
with it. You can reuse the same template to render it several times with
different contexts.
class Context(dict_=None, autoescape=True, use_l10n=None, use_tz=None)[source]
The constructor of django.template.Context takes an optional argument —
a dictionary mapping variable names to variable values.
Three optional keyword arguments can also be specified:
autoescape controls whether HTML autoescaping is enabled.
It defaults to True.
Warning
Only set it to False if you’re rendering non-HTML templates!
use_l10n overrides whether values will be localized by default. If
set to True numbers and dates will be formatted based on locale.
It defaults to None.
See Controlling localization in templates for details.
use_tz overrides whether dates are converted to the local time when
rendered in a template. If set to True all dates will be rendered
using the local timezone. This takes precedence over USE_TZ.
It defaults to None.
See Time zone aware output in templates for details.
For example usage, see Playing with Context objects below.
Template.render(context)[source]
Call the Template object’s render() method with a
Context to “fill” the template:
>>> from django.template import Context, Template
>>> template = Template("My name is {{ my_name }}.")
>>> context = Context({"my_name": "Adrian"})
>>> template.render(context)
"My name is Adrian."
>>> 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.
Dots have a special meaning in template rendering. A dot in a variable name
signifies a lookup. Specifically, when the template system encounters a
dot in a variable name, it tries the following lookups, in this order:
Dictionary lookup. Example: foo["bar"]
Attribute lookup. Example: foo.bar
List-index lookup. Example: foo[bar]
Note that “bar” in a template expression like {{ foo.bar }} will be
interpreted as a literal string and not using the value of the variable “bar”,
if one exists in the template context.
The template system uses the first lookup type that works. It’s short-circuit
logic. Here are a few examples:
>>> from django.template import Context, Template
>>> t = Template("My name is {{ person.first_name }}.")
>>> d = {"person": {"first_name": "Joe", "last_name": "Johnson"}}
>>> t.render(Context(d))
"My name is Joe."
>>> class PersonClass:
... pass
>>> p = PersonClass()
>>> p.first_name = "Ron"
>>> p.last_name = "Nasty"
>>> t.render(Context({"person": p}))
"My name is Ron."
>>> t = Template("The first stooge in the list is {{ stooges.0 }}.")
>>> c = Context({"stooges": ["Larry", "Curly", "Moe"]})
>>> t.render(c)
"The first stooge in the list is Larry."
If any part of the variable is callable, the template system will try calling
it. Example:
>>> class PersonClass2:
... def name(self):
... return "Samantha"
>>> t = Template("My name is {{ person.name }}.")
>>> t.render(Context({"person": PersonClass2}))
"My name is Samantha."
Callable variables are slightly more complex than variables which only require
straight lookups. Here are some things to keep in mind:
If the variable raises an exception when called, the exception will be
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 engine’s
string_if_invalid configuration option (an empty string, by default).
Example:
>>> t = Template("My name is {{ person.first_name }}.")
>>> class PersonClass3:
... def first_name(self):
... raise AssertionError("foo")
>>> p = PersonClass3()
>>> t.render(Context({"person": p}))
Traceback (most recent call last):
AssertionError: foo
>>> class SilentAssertionError(Exception):
... silent_variable_failure = True
>>> class PersonClass4:
... def first_name(self):
... raise SilentAssertionError
>>> p = PersonClass4()
>>> t.render(Context({"person": p}))
"My name is ."
Note that django.core.exceptions.ObjectDoesNotExist, which is the
base class for all Django database API DoesNotExist exceptions, has
silent_variable_failure = True. So if you’re using Django templates
with Django model objects, any DoesNotExist exception will fail
silently.
A variable can only be called if it has no required arguments. Otherwise,
the system will return the value of the engine’s string_if_invalid
option.
There can be side effects when calling some variables, and it’d be either
foolish or a security hole to allow the template system to access them.
A good example is the delete() method on
each Django model object. The template system shouldn’t be allowed to do
something like this:
I will now delete this valuable data. {{ data.delete }}
To prevent this, set an alters_data attribute on the callable
variable. The template system won’t call a variable if it has
alters_data=True set, and will instead replace the variable with
string_if_invalid, unconditionally. The
dynamically-generated delete() and
save() methods on Django model objects get
alters_data=True automatically. Example:
def sensitive_function(self):
self.database_record.delete()
sensitive_function.alters_data = True
Occasionally you may want to turn off this feature for other reasons,
and tell the template system to leave a variable uncalled no matter
what. To do so, set a do_not_call_in_templates attribute on the
callable with the value True. The template system then will act as
if your variable is not callable (allowing you to access attributes of
the callable, for example).
How invalid variables are handled
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
string_if_invalid is set to '' (the empty string). If
string_if_invalid is set to any other value, variable filters will be
ignored.
This behavior is slightly different for the if, for and regroup
template tags. If an invalid variable is provided to one of these template
tags, the variable will be interpreted as None. Filters are always
applied to invalid variables within these template tags.
If string_if_invalid contains a '%s', the format marker will be
replaced with the name of the invalid variable.
For debug purposes only!
While string_if_invalid can be a useful debugging tool, it is a bad
idea to turn it on as a ‘development default’.
Many templates, including some of Django’s, rely upon the silence of the
template system when a nonexistent variable is encountered. If you assign a
value other than '' to string_if_invalid, you will experience
rendering problems with these templates and sites.
Generally, string_if_invalid should only be enabled in order to debug
a specific template problem, then cleared once debugging is complete.
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 templatetag tag is required if you need to
output character sequences like {% and %}.
A similar issue exists if you want to include these sequences in template filter
or tag arguments. For example, when parsing a block tag, Django’s template
parser looks for the first occurrence of %} after a {%. This prevents
the use of "%}" as a string literal. For example, a TemplateSyntaxError
will be raised for the following expressions:
{% include "template.html" tvar="Some string literal with %} in it." %}
{% with tvar="Some string literal with %} in it." %}{% endwith %}
The same issue can be triggered by using a reserved sequence in filter
arguments:
{{ some.variable|default:"}}" }}
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
Most of the time, you’ll instantiate 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:
>>> from django.template import Context
>>> c = Context({"foo": "bar"})
>>> c["foo"]
'bar'
>>> del c["foo"]
>>> c["foo"]
Traceback (most recent call last):
KeyError: 'foo'
>>> c["newvariable"] = "hello"
>>> c["newvariable"]
'hello'
Context.get(key, otherwise=None)
Returns the value for key if key is in the context, else returns
otherwise.
Context.setdefault(key, default=None)
If key is in the context, returns its value. Otherwise inserts key
with a value of default and returns default.
A Context object is a stack. That is, you can push() and pop() it.
If you pop() too much, it’ll raise
django.template.ContextPopException:
>>> c = Context()
>>> c["foo"] = "first level"
>>> c.push()
>>> c["foo"] = "second level"
>>> c["foo"]
'second level'
>>> c.pop()
{'foo': 'second level'}
>>> c["foo"]
'first level'
>>> c["foo"] = "overwritten"
>>> c["foo"]
'overwritten'
>>> c.pop()
Traceback (most recent call last):
ContextPopException
You can also use push() as a context manager to ensure a matching pop()
is called.
>>> c = Context()
>>> c["foo"] = "first level"
>>> with c.push():
... c["foo"] = "second level"
... c["foo"]
'second level'
>>> c["foo"]
'first level'
All arguments passed to push() will be passed to the dict constructor
used to build the new context level.
>>> c = Context()
>>> c["foo"] = "first level"
>>> with c.push(foo="second level"):
... c["foo"]
'second level'
>>> c["foo"]
'first level'
In addition to push() and pop(), the Context
object also defines an update() method. This works like push()
but takes a dictionary as an argument and pushes that dictionary onto
the stack instead of an empty one.
>>> c = Context()
>>> c["foo"] = "first level"
>>> c.update({"foo": "updated"})
{'foo': 'updated'}
>>> c["foo"]
'updated'
>>> c.pop()
{'foo': 'updated'}
>>> c["foo"]
'first level'
Like push(), you can use update() as a context manager to ensure a
matching pop() is called.
>>> c = Context()
>>> c["foo"] = "first level"
>>> with c.update({"foo": "second level"}):
... c["foo"]
'second level'
>>> c["foo"]
'first level'
Using a Context as a stack comes in handy in some custom template
tags.
Context.flatten()
Using flatten() method you can get whole Context stack as one dictionary
including builtin variables.
>>> c = Context()
>>> c["foo"] = "first level"
>>> c.update({"bar": "second level"})
{'bar': 'second level'}
>>> c.flatten()
{'True': True, 'None': None, 'foo': 'first level', 'False': False, 'bar': 'second level'}
A flatten() method is also internally used to make Context objects comparable.
>>> c1 = Context()
>>> c1["foo"] = "first level"
>>> c1["bar"] = "second level"
>>> c2 = Context()
>>> c2.update({"bar": "second level", "foo": "first level"})
{'foo': 'first level', 'bar': 'second level'}
>>> c1 == c2
Result from flatten() can be useful in unit tests to compare Context
against dict:
class ContextTest(unittest.TestCase):
def test_against_dictionary(self):
c1 = Context()
c1["update"] = "value"
self.assertEqual(
c1.flatten(),
"True": True,
"None": None,
"False": False,
"update": "value",
Using RequestContext
class RequestContext(request, dict_=None, processors=None, use_l10n=None, use_tz=None, autoescape=True)[source]
Django comes with a special Context class,
django.template.RequestContext, that acts slightly differently from the
normal django.template.Context. The first difference is that it takes an
HttpRequest as its first argument. For example:
c = RequestContext(
request,
"foo": "bar",
The second difference is that it automatically populates the context with a
few variables, according to the engine’s context_processors configuration
option.
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
processors:
"django.template.context_processors.debug",
"django.template.context_processors.request",
"django.contrib.auth.context_processors.auth",
"django.contrib.messages.context_processors.messages",
In addition to these, 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
name, the second will override the first. The default processors are explained
below.
When context processors are applied
Context processors are applied on top of context data. 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.
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"})
Django does this to allow context data to override context processors in
APIs such as render() and
TemplateResponse.
Also, you can give RequestContext a list of additional processors,
using the optional, third positional argument, processors. In this
example, the RequestContext instance gets an ip_address variable:
from django.http import HttpResponse
from django.template import RequestContext, Template
def ip_address_processor(request):
return {"ip_address": request.META["REMOTE_ADDR"]}
def client_ip_view(request):
template = Template("{{ title }}: {{ ip_address }}")
context = RequestContext(
request,
"title": "Your IP Address",
[ip_address_processor],
return HttpResponse(template.render(context))
Here’s what each of the built-in processors does:
django.contrib.auth.context_processors.auth
auth(request)[source]
If this processor is enabled, every RequestContext will contain these
variables:
user – An auth.User instance representing the currently
logged-in user (or an AnonymousUser instance, if the client isn’t
logged in).
perms – An instance of
django.contrib.auth.context_processors.PermWrapper, representing the
permissions that the currently logged-in user has.
django.template.context_processors.debug
debug(request)[source]
If this processor is enabled, every RequestContext will contain these two
variables – but only if your DEBUG setting is set to True and
the request’s IP address (request.META['REMOTE_ADDR']) is in the
INTERNAL_IPS setting:
debug – True. You can use this in templates to test whether
you’re in DEBUG mode.
sql_queries – A list of {'sql': ..., 'time': ...} dictionaries,
representing every SQL query that has happened so far during the request
and how long it took. The list is in order by database alias and then by
query. It’s lazily generated on access.
django.template.context_processors.i18n
i18n(request)[source]
If this processor is enabled, every RequestContext will contain these
variables:
LANGUAGES – The value of the LANGUAGES setting.
LANGUAGE_BIDI – True if the current language is a right-to-left
language, e.g. Hebrew, Arabic. False if it’s a left-to-right language,
e.g. English, French, German.
LANGUAGE_CODE – request.LANGUAGE_CODE, if it exists. Otherwise,
the value of the LANGUAGE_CODE setting.
See i18n template tags for template tags that
generate the same values.
django.template.context_processors.media
If this processor is enabled, every RequestContext will contain a variable
MEDIA_URL, providing the value of the MEDIA_URL setting.
django.template.context_processors.static
static(request)[source]
If this processor is enabled, every RequestContext will contain a variable
STATIC_URL, providing the value of the STATIC_URL setting.
django.template.context_processors.csrf
This processor adds a token that is needed by the csrf_token template
tag for protection against Cross Site Request Forgeries.
django.template.context_processors.request
If this processor is enabled, every RequestContext will contain a variable
request, which is the current HttpRequest.
django.template.context_processors.tz
tz(request)[source]
If this processor is enabled, every RequestContext will contain a variable
TIME_ZONE, providing the name of the currently active time zone.
django.contrib.messages.context_processors.messages
If this processor is enabled, every RequestContext will contain these two
variables:
messages – A list of messages (as strings) that have been set
via the messages framework.
DEFAULT_MESSAGE_LEVELS – A mapping of the message level names to
their numeric value.
Writing your own context processors
A context processor has a simple interface: It’s a Python function that takes
one argument, an HttpRequest object, and returns a
dictionary that gets added to the template context.
For example, to add the DEFAULT_FROM_EMAIL setting to every
context:
from django.conf import settings
def from_email(request):
return {
"DEFAULT_FROM_EMAIL": settings.DEFAULT_FROM_EMAIL,
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 TEMPLATES setting — or the
context_processors argument of 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.
Django searches for template directories in a number of places, depending on
your template loading settings (see “Loader types” below), but the most basic
way of specifying template directories is by using the DIRS option.
The DIRS option
Tell Django what your template directories are by using the DIRS option in the TEMPLATES setting in your settings
file — or the dirs argument of Engine. This
should be set to a list of strings that contain full paths to your template
directories:
TEMPLATES = [
"BACKEND": "django.template.backends.django.DjangoTemplates",
"DIRS": [
"/home/html/templates/lawrence.com",
"/home/html/templates/default",
Your templates can go anywhere you want, as long as the directories and
templates are readable by the web server. They can have any extension you want,
such as .html or .txt, or they can have no extension at all.
Note that these paths should use Unix-style forward slashes, even on Windows.
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
sources.
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
TEMPLATES setting or passing a loaders argument to
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:
django.template.loaders.filesystem.Loader
class filesystem.Loader
Loads templates from the filesystem, according to
DIRS.
This loader is enabled by default. However it won’t find any templates
until you set DIRS to a non-empty list:
TEMPLATES = [
"BACKEND": "django.template.backends.django.DjangoTemplates",
"DIRS": [BASE_DIR / "templates"],
You can also override 'DIRS' and specify specific directories for a
particular filesystem loader:
TEMPLATES = [
"BACKEND": "django.template.backends.django.DjangoTemplates",
"OPTIONS": {
"loaders": [
"django.template.loaders.filesystem.Loader",
[BASE_DIR / "templates"],
class app_directories.Loader
Loads templates from Django apps on the filesystem. For each app in
INSTALLED_APPS, the loader looks for a templates
subdirectory. If the directory exists, Django looks for templates in there.
This means you can store templates with your individual apps. This also
helps to distribute Django apps with default templates.
For example, for this setting:
INSTALLED_APPS = ["myproject.polls", "myproject.music"]
…then get_template('foo.html') will look for foo.html in these
directories, in this order:
/path/to/myproject/polls/templates/
/path/to/myproject/music/templates/
… and will use the one it finds first.
The order of INSTALLED_APPS is significant! For example, if you
want to customize the Django admin, you might choose to override the
standard admin/base_site.html template, from django.contrib.admin,
with your own admin/base_site.html in myproject.polls. You must
then make sure that your myproject.polls comes before
django.contrib.admin in INSTALLED_APPS, otherwise
django.contrib.admin’s will be loaded first and yours will be ignored.
Note that the loader performs an optimization when it first runs:
it caches a list of which INSTALLED_APPS packages have a
templates subdirectory.
You can enable this loader by setting APP_DIRS to True:
TEMPLATES = [
"BACKEND": "django.template.backends.django.DjangoTemplates",
"APP_DIRS": True,
class cached.Loader
While the Django template system is quite fast, if it needs to read and
compile your templates every time they’re rendered, the overhead from that
can add up.
You configure the cached template loader with a list of other loaders that
it should wrap. The wrapped loaders are used to locate unknown templates
when they’re first encountered. The cached loader then stores the compiled
Template in memory. The cached Template instance is returned for
subsequent requests to load the same template.
This loader is automatically enabled if OPTIONS['loaders'] isn’t specified.
You can manually specify template caching with some custom template loaders
using settings like this:
TEMPLATES = [
"BACKEND": "django.template.backends.django.DjangoTemplates",
"DIRS": [BASE_DIR / "templates"],
"OPTIONS": {
"loaders": [
"django.template.loaders.cached.Loader",
"django.template.loaders.filesystem.Loader",
"django.template.loaders.app_directories.Loader",
"path.to.custom.Loader",
All of the built-in Django template tags are safe to use with the
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 template tag thread safety considerations.
django.template.loaders.locmem.Loader
class locmem.Loader
Loads templates from a Python dictionary. This is useful for testing.
This loader takes a dictionary of templates as its first argument:
TEMPLATES = [
"BACKEND": "django.template.backends.django.DjangoTemplates",
"OPTIONS": {
"loaders": [
"django.template.loaders.locmem.Loader",
"index.html": "content here",
This loader is disabled by default.
Django uses the template loaders in order according to the 'loaders'
option. It uses each loader until a loader finds a match.
Custom loaders
It’s possible to load templates from additional sources using custom template
loaders. Custom Loader classes should inherit from
django.template.loaders.base.Loader and define the get_contents() and
get_template_sources() methods.
Loader methods
class Loader[source]
Loads templates from a given source, such as the filesystem or a database.
get_template_sources(template_name)[source]
A method that takes a template_name and yields
Origin instances for each possible
source.
For example, the filesystem loader may receive 'index.html' as a
template_name argument. This method would yield origins for the
full path of index.html as it appears in each template directory
the loader looks at.
The method doesn’t need to verify that the template exists at a given
path, but it should ensure the path is valid. For instance, the
filesystem loader makes sure the path lies under a valid template
directory.
Returns the contents for a template given a
Origin instance.
This is where a filesystem loader would read contents from the
filesystem, or a database loader would read from the database. If a
matching template doesn’t exist, this should raise a
TemplateDoesNotExist error.
get_template(template_name, skip=None)[source]
Returns a Template object for a given template_name by looping
through results from get_template_sources() and calling
get_contents(). This returns the first matching template. If no
template is found, TemplateDoesNotExist is
raised.
The optional skip argument is a list of origins to ignore when
extending templates. This allow templates to extend other templates of
the same name. It also used to avoid recursion errors.
In general, it is enough to define get_template_sources() and
get_contents() for custom template loaders. get_template()
will usually not need to be overridden.
Template origin
Templates have an origin containing attributes depending on the source
they are loaded from.
class Origin(name, template_name=None, loader=None)[source]
name
The path to the template as returned by the template loader.
For loaders that read from the file system, this is the full
path to the template.
If the template is instantiated directly rather than through a
template loader, this is a string value of <unknown_source>.
The relative path to the template as passed into the
template loader.
If the template is instantiated directly rather than through a
template loader, this is None.
loader
The template loader instance that constructed this Origin.
If the template is instantiated directly rather than through a
template loader, this is None.
django.template.loaders.cached.Loader requires all of its
wrapped loaders to set this attribute, typically by instantiating
the Origin with loader=self.
Using RequestContext
Built-in template context processors
