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============
Django Utils
============
.. module:: django.utils
:synopsis: Django's built-in utilities.
This document covers all stable modules in ``django.utils``. Most of the
modules in ``django.utils`` are designed for internal use and only the
following parts can be considered stable and thus backwards compatible as per
the :ref:`internal release deprecation policy <internal-release-deprecation-policy>`.
``django.utils.cache``
======================
.. module:: django.utils.cache
:synopsis: Helper functions for controlling caching.
This module contains helper functions for controlling caching. It does so by
managing the ``Vary`` header of responses. It includes functions to patch the
header of response objects directly and decorators that change functions to do
that header-patching themselves.
For information on the ``Vary`` header, see :rfc:`2616#section-14.44` section
14.44.
Essentially, the ``Vary`` HTTP header defines which headers a cache should take
into account when building its cache key. Requests with the same path but
different header content for headers named in ``Vary`` need to get different
cache keys to prevent delivery of wrong content.
For example, :doc:`internationalization </topics/i18n/index>` middleware would
need to distinguish caches by the ``Accept-language`` header.
.. function:: patch_cache_control(response, **kwargs)
This function patches the ``Cache-Control`` header by adding all keyword
arguments to it. The transformation is as follows:
* All keyword parameter names are turned to lowercase, and underscores
are converted to hyphens.
* If the value of a parameter is ``True`` (exactly ``True``, not just a
true value), only the parameter name is added to the header.
* All other parameters are added with their value, after applying
``str()`` to it.
.. function:: get_max_age(response)
Returns the max-age from the response Cache-Control header as an integer
(or ``None`` if it wasn't found or wasn't an integer).
.. function:: patch_response_headers(response, cache_timeout=None)
Adds some useful headers to the given ``HttpResponse`` object:
* ``ETag``
* ``Last-Modified``
* ``Expires``
* ``Cache-Control``
Each header is only added if it isn't already set.
``cache_timeout`` is in seconds. The :setting:`CACHE_MIDDLEWARE_SECONDS`
setting is used by default.
.. function:: add_never_cache_headers(response)
Adds headers to a response to indicate that a page should never be cached.
.. function:: patch_vary_headers(response, newheaders)
Adds (or updates) the ``Vary`` header in the given ``HttpResponse`` object.
``newheaders`` is a list of header names that should be in ``Vary``.
Existing headers in ``Vary`` aren't removed.
.. function:: get_cache_key(request, key_prefix=None)
Returns a cache key based on the request path. It can be used in the
request phase because it pulls the list of headers to take into account
from the global path registry and uses those to build a cache key to
check against.
If there is no headerlist stored, the page needs to be rebuilt, so this
function returns ``None``.
.. function:: learn_cache_key(request, response, cache_timeout=None, key_prefix=None)
Learns what headers to take into account for some request path from the
response object. It stores those headers in a global path registry so that
later access to that path will know what headers to take into account
without building the response object itself. The headers are named in
the ``Vary`` header of the response, but we want to prevent response
generation.
The list of headers to use for cache key generation is stored in the same
cache as the pages themselves. If the cache ages some data out of the
cache, this just means that we have to build the response once to get at
the Vary header and so at the list of headers to use for the cache key.
``django.utils.datastructures``
===============================
.. module:: django.utils.datastructures
:synopsis: Data structures that aren't in Python's standard library.
.. class:: SortedDict
.. deprecated:: 1.7
``SortedDict`` is deprecated and will be removed in Django 1.9. Use
:class:`collections.OrderedDict` instead.
The :class:`django.utils.datastructures.SortedDict` class is a dictionary
that keeps its keys in the order in which they're inserted.
Creating a new SortedDict
-------------------------
Creating a new ``SortedDict`` must be done in a way where ordering is
guaranteed. For example::
SortedDict({'b': 1, 'a': 2, 'c': 3})
will not work. Passing in a basic Python ``dict`` could produce unreliable
results. Instead do::
SortedDict([('b', 1), ('a', 2), ('c', 3)])
``django.utils.dateparse``
==========================
.. module:: django.utils.dateparse
:synopsis: Functions to parse datetime objects.
The functions defined in this module share the following properties:
- They raise :exc:`ValueError` if their input is well formatted but isn't a
valid date or time.
- They return ``None`` if it isn't well formatted at all.
- They accept up to picosecond resolution in input, but they truncate it to
microseconds, since that's what Python supports.
.. function:: parse_date(value)
Parses a string and returns a :class:`datetime.date`.
.. function:: parse_time(value)
Parses a string and returns a :class:`datetime.time`.
UTC offsets aren't supported; if ``value`` describes one, the result is
``None``.
.. function:: parse_datetime(value)
Parses a string and returns a :class:`datetime.datetime`.
UTC offsets are supported; if ``value`` describes one, the result's
``tzinfo`` attribute is a :class:`~django.utils.tzinfo.FixedOffset`
instance.
``django.utils.decorators``
===========================
.. module:: django.utils.decorators
:synopsis: Functions that help with creating decorators for views.
.. function:: method_decorator(decorator)
Converts a function decorator into a method decorator. See :ref:`decorating
class based views<decorating-class-based-views>` for example usage.
.. function:: decorator_from_middleware(middleware_class)
Given a middleware class, returns a view decorator. This lets you use
middleware functionality on a per-view basis. The middleware is created
with no params passed.
.. function:: decorator_from_middleware_with_args(middleware_class)
Like ``decorator_from_middleware``, but returns a function
that accepts the arguments to be passed to the middleware_class.
For example, the :func:`~django.views.decorators.cache.cache_page`
decorator is created from the ``CacheMiddleware`` like this::
cache_page = decorator_from_middleware_with_args(CacheMiddleware)
@cache_page(3600)
def my_view(request):
pass
``django.utils.encoding``
=========================
.. module:: django.utils.encoding
:synopsis: A series of helper functions to manage character encoding.
.. function:: python_2_unicode_compatible
A decorator that defines ``__unicode__`` and ``__str__`` methods under
Python 2. Under Python 3 it does nothing.
To support Python 2 and 3 with a single code base, define a ``__str__``
method returning text and apply this decorator to the class.
.. function:: smart_text(s, encoding='utf-8', strings_only=False, errors='strict')
Returns a text object representing ``s`` -- ``unicode`` on Python 2 and
``str`` on Python 3. Treats bytestrings using the ``encoding`` codec.
If ``strings_only`` is ``True``, don't convert (some) non-string-like
objects.
.. function:: smart_unicode(s, encoding='utf-8', strings_only=False, errors='strict')
Historical name of :func:`smart_text`. Only available under Python 2.
.. function:: is_protected_type(obj)
Determine if the object instance is of a protected type.
Objects of protected types are preserved as-is when passed to
``force_text(strings_only=True)``.
.. function:: force_text(s, encoding='utf-8', strings_only=False, errors='strict')
Similar to ``smart_text``, except that lazy instances are resolved to
strings, rather than kept as lazy objects.
If ``strings_only`` is ``True``, don't convert (some) non-string-like
objects.
.. function:: force_unicode(s, encoding='utf-8', strings_only=False, errors='strict')
Historical name of :func:`force_text`. Only available under Python 2.
.. function:: smart_bytes(s, encoding='utf-8', strings_only=False, errors='strict')
Returns a bytestring version of ``s``, encoded as specified in
``encoding``.
If ``strings_only`` is ``True``, don't convert (some) non-string-like
objects.
.. function:: force_bytes(s, encoding='utf-8', strings_only=False, errors='strict')
Similar to ``smart_bytes``, except that lazy instances are resolved to
bytestrings, rather than kept as lazy objects.
If ``strings_only`` is ``True``, don't convert (some) non-string-like
objects.
.. function:: smart_str(s, encoding='utf-8', strings_only=False, errors='strict')
Alias of :func:`smart_bytes` on Python 2 and :func:`smart_text` on Python
3. This function returns a ``str`` or a lazy string.
For instance, this is suitable for writing to :data:`sys.stdout` on
Python 2 and 3.
.. function:: force_str(s, encoding='utf-8', strings_only=False, errors='strict')
Alias of :func:`force_bytes` on Python 2 and :func:`force_text` on Python
3. This function always returns a ``str``.
.. function:: iri_to_uri(iri)
Convert an Internationalized Resource Identifier (IRI) portion to a URI
portion that is suitable for inclusion in a URL.
This is the algorithm from section 3.1 of :rfc:`3987#section-3.1`. However,
since we are assuming input is either UTF-8 or unicode already, we can
simplify things a little from the full method.
Returns an ASCII string containing the encoded result.
.. function:: filepath_to_uri(path)
Convert a file system path to a URI portion that is suitable for inclusion
in a URL. The path is assumed to be either UTF-8 or unicode.
This method will encode certain characters that would normally be
recognized as special characters for URIs. Note that this method does not
encode the ' character, as it is a valid character within URIs. See
``encodeURIComponent()`` JavaScript function for more details.
Returns an ASCII string containing the encoded result.
``django.utils.feedgenerator``
==============================
.. module:: django.utils.feedgenerator
:synopsis: Syndication feed generation library -- used for generating RSS, etc.
Sample usage::
>>> from django.utils import feedgenerator
>>> feed = feedgenerator.Rss201rev2Feed(
... title="Poynter E-Media Tidbits",
... link="http://www.poynter.org/column.asp?id=31",
... description="A group Weblog by the sharpest minds in online media/journalism/publishing.",
... language="en",
... )
>>> feed.add_item(
... title="Hello",
... link="http://www.holovaty.com/test/",
... description="Testing."
... )
>>> with open('test.rss', 'w') as fp:
... feed.write(fp, 'utf-8')
For simplifying the selection of a generator use ``feedgenerator.DefaultFeed``
which is currently ``Rss201rev2Feed``
For definitions of the different versions of RSS, see:
http://web.archive.org/web/20110718035220/http://diveintomark.org/archives/2004/02/04/incompatible-rss
.. function:: get_tag_uri(url, date)
Creates a TagURI.
See http://web.archive.org/web/20110514113830/http://diveintomark.org/archives/2004/05/28/howto-atom-id
SyndicationFeed
---------------
.. class:: SyndicationFeed
Base class for all syndication feeds. Subclasses should provide write().
.. method:: __init__(title, link, description, [language=None, author_email=None, author_name=None, author_link=None, subtitle=None, categories=None, feed_url=None, feed_copyright=None, feed_guid=None, ttl=None, **kwargs])
Initialize the feed with the given dictionary of metadata, which applies
to the entire feed.
Any extra keyword arguments you pass to ``__init__`` will be stored in
``self.feed``.
All parameters should be Unicode objects, except ``categories``, which
should be a sequence of Unicode objects.
.. method:: add_item(title, link, description, [author_email=None, author_name=None, author_link=None, pubdate=None, comments=None, unique_id=None, enclosure=None, categories=(), item_copyright=None, ttl=None, updateddate=None, **kwargs])
Adds an item to the feed. All args are expected to be Python ``unicode``
objects except ``pubdate`` and ``updateddate``, which are ``datetime.datetime``
objects, and ``enclosure``, which is an instance of the ``Enclosure`` class.
.. versionadded:: 1.7
The optional ``updateddate`` argument was added.
.. method:: num_items()
.. method:: root_attributes()
Return extra attributes to place on the root (i.e. feed/channel)
element. Called from ``write()``.
.. method:: add_root_elements(handler)
Add elements in the root (i.e. feed/channel) element.
Called from ``write()``.
.. method:: item_attributes(item)
Return extra attributes to place on each item (i.e. item/entry)
element.
.. method:: add_item_elements(handler, item)
Add elements on each item (i.e. item/entry) element.
.. method:: write(outfile, encoding)
Outputs the feed in the given encoding to ``outfile``, which is a
file-like object. Subclasses should override this.
.. method:: writeString(encoding)
Returns the feed in the given encoding as a string.
.. method:: latest_post_date()
Returns the latest ``pubdate`` or ``updateddate`` for all items in the
feed. If no items have either of these attributes this returns the
current date/time.
Enclosure
---------
.. class:: Enclosure
Represents an RSS enclosure
RssFeed
-------
.. class:: RssFeed(SyndicationFeed)
Rss201rev2Feed
--------------
.. class:: Rss201rev2Feed(RssFeed)
Spec: http://cyber.law.harvard.edu/rss/rss.html
RssUserland091Feed
------------------
.. class:: RssUserland091Feed(RssFeed)
Spec: http://backend.userland.com/rss091
Atom1Feed
---------
.. class:: Atom1Feed(SyndicationFeed)
Spec: http://tools.ietf.org/html/rfc4287
``django.utils.functional``
===========================
.. module:: django.utils.functional
:synopsis: Functional programming tools.
.. class:: cached_property(object)
The ``@cached_property`` decorator caches the result of a method with a
single ``self`` argument as a property. The cached result will persist
as long as the instance does, so if the instance is passed around and the
function subsequently invoked, the cached result will be returned.
Consider a typical case, where a view might need to call a model's method
to perform some computation, before placing the model instance into the
context, where the template might invoke the method once more:
.. code-block:: python
# the model
class Person(models.Model):
def friends(self):
# expensive computation
...
return friends
# in the view:
if person.friends():
# in the template:
{% for friend in person.friends %}
Here, ``friends()`` will be called twice. Since the instance ``person`` in
the view and the template are the same, ``@cached_property`` can avoid
that::
from django.utils.functional import cached_property
@cached_property
def friends(self):
# expensive computation
...
return friends
Note that as the method is now a property, in Python code it will need to
be invoked appropriately::
# in the view:
if person.friends:
The cached value can be treated like an ordinary attribute of the instance::
# clear it, requiring re-computation next time it's called
del person.friends # or delattr(person, "friends")
# set a value manually, that will persist on the instance until cleared
person.friends = ["Huckleberry Finn", "Tom Sawyer"]
As well as offering potential performance advantages, ``@cached_property``
can ensure that an attribute's value does not change unexpectedly over the
life of an instance. This could occur with a method whose computation is
based on ``datetime.now()``, or simply if a change were saved to the
database by some other process in the brief interval between subsequent
invocations of a method on the same instance.
.. function:: allow_lazy(func, *resultclasses)
Django offers many utility functions (particularly in ``django.utils``)
that take a string as their first argument and do something to that string.
These functions are used by template filters as well as directly in other
code.
If you write your own similar functions and deal with translations, you'll
face the problem of what to do when the first argument is a lazy
translation object. You don't want to convert it to a string immediately,
because you might be using this function outside of a view (and hence the
current thread's locale setting will not be correct).
For cases like this, use the ``django.utils.functional.allow_lazy()``
decorator. It modifies the function so that *if* it's called with a lazy
translation as one of its arguments, the function evaluation is delayed
until it needs to be converted to a string.
For example::
from django.utils.functional import allow_lazy
def fancy_utility_function(s, ...):
# Do some conversion on string 's'
...
# Replace unicode by str on Python 3
fancy_utility_function = allow_lazy(fancy_utility_function, unicode)
The ``allow_lazy()`` decorator takes, in addition to the function to
decorate, a number of extra arguments (``*args``) specifying the type(s)
that the original function can return. Usually, it's enough to include
``unicode`` (or ``str`` on Python 3) here and ensure that your function
returns only Unicode strings.
Using this decorator means you can write your function and assume that the
input is a proper string, then add support for lazy translation objects at
the end.
``django.utils.html``
=====================
.. module:: django.utils.html
:synopsis: HTML helper functions
Usually you should build up HTML using Django's templates to make use of its
autoescape mechanism, using the utilities in :mod:`django.utils.safestring`
where appropriate. This module provides some additional low level utilities for
escaping HTML.
.. function:: escape(text)
Returns the given text with ampersands, quotes and angle brackets encoded
for use in HTML. The input is first passed through
:func:`~django.utils.encoding.force_text` and the output has
:func:`~django.utils.safestring.mark_safe` applied.
.. function:: conditional_escape(text)
Similar to ``escape()``, except that it doesn't operate on pre-escaped
strings, so it will not double escape.
.. function:: format_html(format_string, *args, **kwargs)
This is similar to `str.format`_, except that it is appropriate for
building up HTML fragments. All args and kwargs are passed through
:func:`conditional_escape` before being passed to ``str.format``.
For the case of building up small HTML fragments, this function is to be
preferred over string interpolation using ``%`` or ``str.format`` directly,
because it applies escaping to all arguments - just like the Template system
applies escaping by default.
So, instead of writing:
.. code-block:: python
mark_safe("%s <b>%s</b> %s" % (some_html,
escape(some_text),
escape(some_other_text),
))
you should instead use:
.. code-block:: python
format_html("{0} <b>{1}</b> {2}",
mark_safe(some_html), some_text, some_other_text)
This has the advantage that you don't need to apply :func:`escape` to each
argument and risk a bug and an XSS vulnerability if you forget one.
Note that although this function uses ``str.format`` to do the
interpolation, some of the formatting options provided by `str.format`_
(e.g. number formatting) will not work, since all arguments are passed
through :func:`conditional_escape` which (ultimately) calls
:func:`~django.utils.encoding.force_text` on the values.
.. function:: format_html_join(sep, format_string, args_generator)
A wrapper of :func:`format_html`, for the common case of a group of
arguments that need to be formatted using the same format string, and then
joined using ``sep``. ``sep`` is also passed through
:func:`conditional_escape`.
``args_generator`` should be an iterator that returns the sequence of
``args`` that will be passed to :func:`format_html`. For example::
format_html_join('\n', "<li>{0} {1}</li>", ((u.first_name, u.last_name)
for u in users))
.. function:: strip_tags(value)
Tries to remove anything that looks like an HTML tag from the string, that
is anything contained within ``<>``.
Absolutely NO guaranty is provided about the resulting string being entirely
HTML safe. So NEVER mark safe the result of a ``strip_tag`` call without
escaping it first, for example with :func:`~django.utils.html.escape`.
For example::
strip_tags(value)
If ``value`` is ``"<b>Joel</b> <button>is</button> a <span>slug</span>"``
the return value will be ``"Joel is a slug"``.
If you are looking for a more robust solution, take a look at the `bleach`_
Python library.
.. _bleach: https://pypi.python.org/pypi/bleach
.. function:: remove_tags(value, tags)
Removes a space-separated list of [X]HTML tag names from the output.
For example::
remove_tags(value, "b span")
If ``value`` is ``"<b>Joel</b> <button>is</button> a <span>slug</span>"``
the return value will be ``"Joel <button>is</button> a slug"``.
Note that this filter is case-sensitive.
If ``value`` is ``"<B>Joel</B> <button>is</button> a <span>slug</span>"``
the return value will be ``"<B>Joel</B> <button>is</button> a slug"``.
.. _str.format: http://docs.python.org/library/stdtypes.html#str.format
``django.utils.http``
=====================
.. module:: django.utils.http
:synopsis: HTTP helper functions. (URL encoding, cookie handling, ...)
.. function:: urlquote(url, safe='/')
A version of Python's ``urllib.quote()`` function that can operate on
unicode strings. The url is first UTF-8 encoded before quoting. The
returned string can safely be used as part of an argument to a subsequent
``iri_to_uri()`` call without double-quoting occurring. Employs lazy
execution.
.. function:: urlquote_plus(url, safe='')
A version of Python's urllib.quote_plus() function that can operate on
unicode strings. The url is first UTF-8 encoded before quoting. The
returned string can safely be used as part of an argument to a subsequent
``iri_to_uri()`` call without double-quoting occurring. Employs lazy
execution.
.. function:: urlencode(query, doseq=0)
A version of Python's urllib.urlencode() function that can operate on
unicode strings. The parameters are first case to UTF-8 encoded strings
and then encoded as per normal.
.. function:: cookie_date(epoch_seconds=None)
Formats the time to ensure compatibility with Netscape's cookie standard.
Accepts a floating point number expressed in seconds since the epoch in
UTC--such as that outputted by ``time.time()``. If set to ``None``,
defaults to the current time.
Outputs a string in the format ``Wdy, DD-Mon-YYYY HH:MM:SS GMT``.
.. function:: http_date(epoch_seconds=None)
Formats the time to match the :rfc:`1123` date format as specified by HTTP
:rfc:`2616#section-3.3.1` section 3.3.1.
Accepts a floating point number expressed in seconds since the epoch in
UTC--such as that outputted by ``time.time()``. If set to ``None``,
defaults to the current time.
Outputs a string in the format ``Wdy, DD Mon YYYY HH:MM:SS GMT``.
.. function:: base36_to_int(s)
Converts a base 36 string to an integer. On Python 2 the output is
guaranteed to be an ``int`` and not a ``long``.
.. function:: int_to_base36(i)
Converts a positive integer to a base 36 string. On Python 2 ``i`` must be
smaller than `sys.maxint`_.
.. _sys.maxint: http://docs.python.org/2/library/sys.html#sys.maxint
.. function:: urlsafe_base64_encode(s)
Encodes a bytestring in base64 for use in URLs, stripping any trailing
equal signs.
.. function:: urlsafe_base64_decode(s)
Decodes a base64 encoded string, adding back any trailing equal signs that
might have been stripped.
``django.utils.module_loading``
===============================
.. module:: django.utils.module_loading
:synopsis: Functions for working with Python modules.
Functions for working with Python modules.
.. function:: import_string(dotted_path)
.. versionadded:: 1.7
Imports a dotted module path and returns the attribute/class designated by
the last name in the path. Raises ``ImportError`` if the import failed. For
example::
from django.utils.module_loading import import_string
ValidationError = import_string('django.core.exceptions.ValidationError')
is equivalent to::
from django.core.exceptions import ValidationError
.. function:: import_by_path(dotted_path, error_prefix='')
.. deprecated:: 1.7
Use :meth:`~django.utils.module_loading.import_string` instead.
Imports a dotted module path and returns the attribute/class designated by
the last name in the path. Raises :exc:`~django.core.exceptions.ImproperlyConfigured`
if something goes wrong.
``django.utils.safestring``
===========================
.. module:: django.utils.safestring
:synopsis: Functions and classes for working with strings that can be displayed safely without further escaping in HTML.
Functions and classes for working with "safe strings": strings that can be
displayed safely without further escaping in HTML. Marking something as a "safe
string" means that the producer of the string has already turned characters
that should not be interpreted by the HTML engine (e.g. '<') into the
appropriate entities.
.. class:: SafeBytes
A ``bytes`` subclass that has been specifically marked as "safe"
(requires no further escaping) for HTML output purposes.
.. class:: SafeString
A ``str`` subclass that has been specifically marked as "safe"
(requires no further escaping) for HTML output purposes. This is
:class:`SafeBytes` on Python 2 and :class:`SafeText` on Python 3.
.. class:: SafeText
A ``str`` (in Python 3) or ``unicode`` (in Python 2) subclass
that has been specifically marked as "safe" for HTML output purposes.
.. class:: SafeUnicode
Historical name of :class:`SafeText`. Only available under Python 2.
.. function:: mark_safe(s)
Explicitly mark a string as safe for (HTML) output purposes. The returned
object can be used everywhere a string or unicode object is appropriate.
Can be called multiple times on a single string.
String marked safe will become unsafe again if modified. For example::
>>> mystr = '<b>Hello World</b> '
>>> mystr = mark_safe(mystr)
>>> type(mystr)
<class 'django.utils.safestring.SafeBytes'>
>>> mystr = mystr.strip() # removing whitespace
>>> type(mystr)
<type 'str'>
.. function:: mark_for_escaping(s)
Explicitly mark a string as requiring HTML escaping upon output. Has no
effect on ``SafeData`` subclasses.
Can be called multiple times on a single string (the resulting escaping is
only applied once).
``django.utils.text``
=====================
.. module:: django.utils.text
:synopsis: Text manipulation.
.. function:: slugify
Converts to lowercase, removes non-word characters (alphanumerics and
underscores) and converts spaces to hyphens. Also strips leading and
trailing whitespace.
For example::
slugify(value)
If ``value`` is ``"Joel is a slug"``, the output will be
``"joel-is-a-slug"``.
``django.utils.translation``
============================
.. module:: django.utils.translation
:synopsis: Internationalization support.
For a complete discussion on the usage of the following see the
:doc:`translation documentation </topics/i18n/translation>`.
.. function:: gettext(message)
Translates ``message`` and returns it in a UTF-8 bytestring
.. function:: ugettext(message)
Translates ``message`` and returns it in a unicode string
.. function:: pgettext(context, message)
Translates ``message`` given the ``context`` and returns
it in a unicode string.
For more information, see :ref:`contextual-markers`.
.. function:: gettext_lazy(message)
.. function:: ugettext_lazy(message)
.. function:: pgettext_lazy(context, message)
Same as the non-lazy versions above, but using lazy execution.
See :ref:`lazy translations documentation <lazy-translations>`.
.. function:: gettext_noop(message)
.. function:: ugettext_noop(message)
Marks strings for translation but doesn't translate them now. This can be
used to store strings in global variables that should stay in the base
language (because they might be used externally) and will be translated
later.
.. function:: ngettext(singular, plural, number)
Translates ``singular`` and ``plural`` and returns the appropriate string
based on ``number`` in a UTF-8 bytestring.
.. function:: ungettext(singular, plural, number)
Translates ``singular`` and ``plural`` and returns the appropriate string
based on ``number`` in a unicode string.
.. function:: npgettext(context, singular, plural, number)
Translates ``singular`` and ``plural`` and returns the appropriate string
based on ``number`` and the ``context`` in a unicode string.
.. function:: ngettext_lazy(singular, plural, number)
.. function:: ungettext_lazy(singular, plural, number)
.. function:: npgettext_lazy(context, singular, plural, number)
Same as the non-lazy versions above, but using lazy execution.
See :ref:`lazy translations documentation <lazy-translations>`.
.. function:: string_concat(*strings)
Lazy variant of string concatenation, needed for translations that are
constructed from multiple parts.
.. function:: activate(language)
Fetches the translation object for a given language and activates it as
the current translation object for the current thread.
.. function:: deactivate()
Deactivates the currently active translation object so that further _ calls
will resolve against the default translation object, again.
.. function:: deactivate_all()
Makes the active translation object a ``NullTranslations()`` instance.
This is useful when we want delayed translations to appear as the original
string for some reason.
.. function:: override(language, deactivate=False)
A Python context manager that uses
:func:`django.utils.translation.activate` to fetch the translation object
for a given language, activates it as the translation object for the
current thread and reactivates the previous active language on exit.
Optionally, it can simply deactivate the temporary translation on exit with
:func:`django.utils.translation.deactivate` if the ``deactivate`` argument
is ``True``. If you pass ``None`` as the language argument, a
``NullTranslations()`` instance is activated within the context.
.. function:: get_language()
Returns the currently selected language code.
.. function:: get_language_bidi()
Returns selected language's BiDi layout:
* ``False`` = left-to-right layout
* ``True`` = right-to-left layout
.. function:: get_language_from_request(request, check_path=False)
Analyzes the request to find what language the user wants the system to
show. Only languages listed in settings.LANGUAGES are taken into account.
If the user requests a sublanguage where we have a main language, we send
out the main language.
If ``check_path`` is ``True``, the function first checks the requested URL
for whether its path begins with a language code listed in the
:setting:`LANGUAGES` setting.
.. function:: to_locale(language)
Turns a language name (en-us) into a locale name (en_US).
.. function:: templatize(src)
Turns a Django template into something that is understood by ``xgettext``.
It does so by translating the Django translation tags into standard
``gettext`` function invocations.
.. data:: LANGUAGE_SESSION_KEY
Session key under which the active language for the current session is
stored.
.. _time-zone-selection-functions:
``django.utils.timezone``
=========================
.. module:: django.utils.timezone
:synopsis: Timezone support.
.. data:: utc
:class:`~datetime.tzinfo` instance that represents UTC.
.. function:: get_fixed_timezone(offset)
.. versionadded:: 1.7
Returns a :class:`~datetime.tzinfo` instance that represents a time zone
with a fixed offset from UTC.
``offset`` is a :class:`datetime.timedelta` or an integer number of
minutes. Use positive values for time zones east of UTC and negative
values for west of UTC.
.. function:: get_default_timezone()
Returns a :class:`~datetime.tzinfo` instance that represents the
:ref:`default time zone <default-current-time-zone>`.
.. function:: get_default_timezone_name()
Returns the name of the :ref:`default time zone
<default-current-time-zone>`.
.. function:: get_current_timezone()
Returns a :class:`~datetime.tzinfo` instance that represents the
:ref:`current time zone <default-current-time-zone>`.
.. function:: get_current_timezone_name()
Returns the name of the :ref:`current time zone
<default-current-time-zone>`.
.. function:: activate(timezone)
Sets the :ref:`current time zone <default-current-time-zone>`. The
``timezone`` argument must be an instance of a :class:`~datetime.tzinfo`
subclass or, if pytz_ is available, a time zone name.
.. function:: deactivate()
Unsets the :ref:`current time zone <default-current-time-zone>`.
.. function:: override(timezone)
This is a Python context manager that sets the :ref:`current time zone
<default-current-time-zone>` on entry with :func:`activate()`, and restores
the previously active time zone on exit. If the ``timezone`` argument is
``None``, the :ref:`current time zone <default-current-time-zone>` is unset
on entry with :func:`deactivate()` instead.
.. function:: localtime(value, timezone=None)
Converts an aware :class:`~datetime.datetime` to a different time zone,
by default the :ref:`current time zone <default-current-time-zone>`.
This function doesn't work on naive datetimes; use :func:`make_aware`
instead.
.. function:: now()
Returns a :class:`~datetime.datetime` that represents the
current point in time. Exactly what's returned depends on the value of
:setting:`USE_TZ`:
* If :setting:`USE_TZ` is ``False``, this will be a
:ref:`naive <naive_vs_aware_datetimes>` datetime (i.e. a datetime
without an associated timezone) that represents the current time
in the system's local timezone.
* If :setting:`USE_TZ` is ``True``, this will be an
:ref:`aware <naive_vs_aware_datetimes>` datetime representing the
current time in UTC. Note that :func:`now` will always return
times in UTC regardless of the value of :setting:`TIME_ZONE`;
you can use :func:`localtime` to convert to a time in the current
time zone.
.. function:: is_aware(value)
Returns ``True`` if ``value`` is aware, ``False`` if it is naive. This
function assumes that ``value`` is a :class:`~datetime.datetime`.
.. function:: is_naive(value)
Returns ``True`` if ``value`` is naive, ``False`` if it is aware. This
function assumes that ``value`` is a :class:`~datetime.datetime`.
.. function:: make_aware(value, timezone)
Returns an aware :class:`~datetime.datetime` that represents the same
point in time as ``value`` in ``timezone``, ``value`` being a naive
:class:`~datetime.datetime`.
This function can raise an exception if ``value`` doesn't exist or is
ambiguous because of DST transitions.
.. function:: make_naive(value, timezone)
Returns an naive :class:`~datetime.datetime` that represents in
``timezone`` the same point in time as ``value``, ``value`` being an
aware :class:`~datetime.datetime`
.. _pytz: http://pytz.sourceforge.net/
``django.utils.tzinfo``
=======================
.. deprecated:: 1.7
Use :mod:`~django.utils.timezone` instead.
.. module:: django.utils.tzinfo
:synopsis: Implementation of ``tzinfo`` classes for use with ``datetime.datetime``.
.. class:: FixedOffset
Fixed offset in minutes east from UTC.
.. deprecated:: 1.7
Use :func:`~django.utils.timezone.get_fixed_timezone` instead.
.. class:: LocalTimezone
Proxy timezone information from time module.
.. deprecated:: 1.7
Use :func:`~django.utils.timezone.get_default_timezone` instead.
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