1 ============

     2 Django Utils

     3 ============

     4 

     5 .. module:: django.utils

     6    :synopsis: Django's built-in utilities.

     7 

     8 This document covers all stable modules in ``django.utils``. Most of the

     9 modules in ``django.utils`` are designed for internal use and only the

    10 following parts can be considered stable and thus backwards compatible as per

    11 the :ref:`internal release deprecation policy <internal-release-deprecation-policy>`.

    12 

    13 ``django.utils.cache``

    14 ======================

    15 

    16 .. module:: django.utils.cache

    17    :synopsis: Helper functions for controlling caching.

    18 

    19 This module contains helper functions for controlling caching. It does so by

    20 managing the ``Vary`` header of responses. It includes functions to patch the

    21 header of response objects directly and decorators that change functions to do

    22 that header-patching themselves.

    23 

    24 For information on the ``Vary`` header, see `RFC 2616 section 14.44`_.

    25 

    26 .. _RFC 2616 section 14.44: http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.44

    27 

    28 Essentially, the ``Vary`` HTTP header defines which headers a cache should take

    29 into account when building its cache key. Requests with the same path but

    30 different header content for headers named in ``Vary`` need to get different

    31 cache keys to prevent delivery of wrong content.

    32 

    33 For example, :doc:`internationalization </topics/i18n/index>` middleware would need

    34 to distinguish caches by the ``Accept-language`` header.

    35 

    36 .. function:: patch_cache_control(response, **kwargs)

    37 

    38 This function patches the ``Cache-Control`` header by adding all keyword

    39 arguments to it. The transformation is as follows:

    40 

    41  * All keyword parameter names are turned to lowercase, and underscores

    42    are converted to hyphens.

    43  * If the value of a parameter is ``True`` (exactly ``True``, not just a

    44    true value), only the parameter name is added to the header.

    45  * All other parameters are added with their value, after applying

    46    ``str()`` to it.

    47 

    48 .. function:: get_max_age(response)

    49 

    50 Returns the max-age from the response Cache-Control header as an integer (or

    51 ``None`` if it wasn't found or wasn't an integer).

    52 

    53 .. function:: patch_response_headers(response, cache_timeout=None)

    54 

    55 Adds some useful headers to the given ``HttpResponse`` object:

    56 

    57  * ``ETag``

    58  * ``Last-Modified``

    59  * ``Expires``

    60  * ``Cache-Control``

    61 

    62 Each header is only added if it isn't already set.

    63 

    64 ``cache_timeout`` is in seconds. The ``CACHE_MIDDLEWARE_SECONDS`` setting is

    65 used by default.

    66 

    67 .. function:: add_never_cache_headers(response)

    68 

    69 Adds headers to a response to indicate that a page should never be cached.

    70 

    71 .. function:: patch_vary_headers(response, newheaders)

    72 

    73 Adds (or updates) the ``Vary`` header in the given ``HttpResponse`` object.

    74 ``newheaders`` is a list of header names that should be in ``Vary``. Existing

    75 headers in ``Vary`` aren't removed.

    76 

    77 .. function:: get_cache_key(request, key_prefix=None)

    78 

    79 Returns a cache key based on the request path. It can be used in the request

    80 phase because it pulls the list of headers to take into account from the

    81 global path registry and uses those to build a cache key to check against.

    82 

    83 If there is no headerlist stored, the page needs to be rebuilt, so this

    84 function returns ``None``.

    85 

    86 .. function:: learn_cache_key(request, response, cache_timeout=None, key_prefix=None)

    87 

    88 Learns what headers to take into account for some request path from the

    89 response object. It stores those headers in a global path registry so that

    90 later access to that path will know what headers to take into account without

    91 building the response object itself. The headers are named in the ``Vary``

    92 header of the response, but we want to prevent response generation.

    93 

    94 The list of headers to use for cache key generation is stored in the same cache

    95 as the pages themselves. If the cache ages some data out of the cache, this

    96 just means that we have to build the response once to get at the Vary header

    97 and so at the list of headers to use for the cache key.

    98 

    99 SortedDict

   100 ==========

   101 

   102 .. module:: django.utils.datastructures

   103    :synopsis: A dictionary that keeps its keys in the order in which they're inserted.

   104 

   105 .. class:: django.utils.datastructures.SortedDict

   106 

   107 Methods

   108 -------

   109 

   110 Extra methods that ``SortedDict`` adds to the standard Python ``dict`` class.

   111 

   112 .. method:: insert(index, key, value)

   113 

   114 Inserts the key, value pair before the item with the given index.

   115 

   116 .. method:: value_for_index(index)

   117 

   118 Returns the value of the item at the given zero-based index.

   119 

   120 Creating new SortedDict

   121 -----------------------

   122 

   123 Creating a new ``SortedDict`` must be done in a way where ordering is

   124 guaranteed. For example::

   125 

   126     SortedDict({'b': 1, 'a': 2, 'c': 3})

   127 

   128 will not work. Passing in a basic Python ``dict`` could produce unreliable

   129 results. Instead do::

   130 

   131     SortedDict([('b', 1), ('a', 2), ('c', 3)])

   132 

   133 ``django.utils.encoding``

   134 =========================

   135 

   136 .. module:: django.utils.encoding

   137    :synopsis: A series of helper classes and function to manage character encoding.

   138 

   139 .. class:: StrAndUnicode

   140 

   141 A class whose ``__str__`` returns its ``__unicode__`` as a UTF-8 bytestring.

   142 Useful as a mix-in.

   143 

   144 .. function:: smart_unicode(s, encoding='utf-8', strings_only=False, errors='strict')

   145 

   146 Returns a ``unicode`` object representing ``s``. Treats bytestrings using the

   147 'encoding' codec.

   148 

   149 If ``strings_only`` is ``True``, don't convert (some) non-string-like objects.

   150 

   151 .. function:: is_protected_type(obj)

   152 

   153 Determine if the object instance is of a protected type.

   154 

   155 Objects of protected types are preserved as-is when passed to

   156 ``force_unicode(strings_only=True)``.

   157 

   158 .. function:: force_unicode(s, encoding='utf-8', strings_only=False, errors='strict')

   159 

   160 Similar to ``smart_unicode``, except that lazy instances are resolved to strings,

   161 rather than kept as lazy objects.

   162 

   163 If ``strings_only`` is ``True``, don't convert (some) non-string-like objects.

   164 

   165 .. function:: smart_str(s, encoding='utf-8', strings_only=False, errors='strict')

   166 

   167 Returns a bytestring version of ``s``, encoded as specified in ``encoding``.

   168 

   169 If ``strings_only`` is ``True``, don't convert (some) non-string-like objects.

   170 

   171 .. function:: iri_to_uri(iri)

   172 

   173 Convert an Internationalized Resource Identifier (IRI) portion to a URI portion

   174 that is suitable for inclusion in a URL.

   175 

   176 This is the algorithm from section 3.1 of `RFC 3987`_.  However, since we are

   177 assuming input is either UTF-8 or unicode already, we can simplify things a

   178 little from the full method.

   179 

   180 .. _RFC 3987: http://www.ietf.org/rfc/rfc3987.txt

   181 

   182 Returns an ASCII string containing the encoded result.

   183 

   184 ``django.utils.feedgenerator``

   185 ==============================

   186 

   187 .. module:: django.utils.feedgenerator

   188    :synopsis: Syndication feed generation library -- used for generating RSS, etc.

   189 

   190 Sample usage::

   191 

   192     >>> from django.utils import feedgenerator

   193     >>> feed = feedgenerator.Rss201rev2Feed(

   194     ...     title=u"Poynter E-Media Tidbits",

   195     ...     link=u"http://www.poynter.org/column.asp?id=31",

   196     ...     description=u"A group Weblog by the sharpest minds in online media/journalism/publishing.",

   197     ...     language=u"en",

   198     ... )

   199     >>> feed.add_item(

   200     ...     title="Hello",

   201     ...     link=u"http://www.holovaty.com/test/",

   202     ...     description="Testing."

   203     ... )

   204     >>> fp = open('test.rss', 'w')

   205     >>> feed.write(fp, 'utf-8')

   206     >>> fp.close()

   207 

   208 For simplifying the selection of a generator use ``feedgenerator.DefaultFeed``

   209 which is currently ``Rss201rev2Feed``

   210 

   211 For definitions of the different versions of RSS, see:

   212 http://diveintomark.org/archives/2004/02/04/incompatible-rss

   213 

   214 .. function:: get_tag_uri(url, date)

   215 

   216 Creates a TagURI.

   217 

   218 See http://diveintomark.org/archives/2004/05/28/howto-atom-id

   219 

   220 SyndicationFeed

   221 ---------------

   222 

   223 .. class:: SyndicationFeed

   224 

   225 Base class for all syndication feeds. Subclasses should provide write().

   226 

   227 Methods

   228 ~~~~~~~

   229 

   230 .. 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, **kwargs])

   231 

   232 Adds an item to the feed. All args are expected to be Python ``unicode``

   233 objects except ``pubdate``, which is a ``datetime.datetime`` object, and

   234 ``enclosure``, which is an instance of the ``Enclosure`` class.

   235 

   236 .. method:: num_items()

   237 

   238 .. method:: root_attributes()

   239 

   240 Return extra attributes to place on the root (i.e. feed/channel) element.

   241 Called from write().

   242 

   243 .. method:: add_root_elements(handler)

   244 

   245 Add elements in the root (i.e. feed/channel) element. Called from write().

   246 

   247 .. method:: item_attributes(item)

   248 

   249 Return extra attributes to place on each item (i.e. item/entry) element.

   250 

   251 .. method:: add_item_elements(handler, item)

   252 

   253 Add elements on each item (i.e. item/entry) element.

   254 

   255 .. method:: write(outfile, encoding)

   256 

   257 Outputs the feed in the given encoding to ``outfile``, which is a file-like

   258 object. Subclasses should override this.

   259 

   260 .. method:: writeString(encoding)

   261 

   262 Returns the feed in the given encoding as a string.

   263 

   264 .. method:: latest_post_date()

   265 

   266 Returns the latest item's ``pubdate``. If none of them have a ``pubdate``,

   267 this returns the current date/time.

   268 

   269 Enclosure

   270 ---------

   271 

   272 .. class:: Enclosure

   273 

   274 Represents an RSS enclosure

   275 

   276 RssFeed

   277 -------

   278 

   279 .. class:: RssFeed(SyndicationFeed)

   280 

   281 Rss201rev2Feed

   282 --------------

   283 

   284 .. class:: Rss201rev2Feed(RssFeed)

   285 

   286 Spec: http://blogs.law.harvard.edu/tech/rss

   287 

   288 Atom1Feed

   289 ---------

   290 

   291 .. class:: Atom1Feed(SyndicationFeed)

   292 

   293 Spec: http://atompub.org/2005/07/11/draft-ietf-atompub-format-10.html

   294 

   295 ``django.utils.http``

   296 =====================

   297 

   298 .. module:: django.utils.http

   299    :synopsis: HTTP helper functions. (URL encoding, cookie handling, ...)

   300 

   301 .. function:: urlquote(url, safe='/')

   302 

   303 A version of Python's ``urllib.quote()`` function that can operate on unicode

   304 strings. The url is first UTF-8 encoded before quoting. The returned string

   305 can safely be used as part of an argument to a subsequent ``iri_to_uri()``

   306 call without double-quoting occurring. Employs lazy execution.

   307 

   308 .. function:: urlquote_plus(url, safe='')

   309 

   310 A version of Python's urllib.quote_plus() function that can operate on unicode

   311 strings. The url is first UTF-8 encoded before quoting. The returned string can

   312 safely be used as part of an argument to a subsequent iri_to_uri() call without

   313 double-quoting occurring. Employs lazy execution.

   314 

   315 .. function:: urlencode(query, doseq=0)

   316 

   317 A version of Python's urllib.urlencode() function that can operate on unicode

   318 strings. The parameters are first case to UTF-8 encoded strings and then

   319 encoded as per normal.

   320 

   321 .. function:: cookie_date(epoch_seconds=None)

   322 

   323 Formats the time to ensure compatibility with Netscape's cookie standard.

   324 

   325 Accepts a floating point number expressed in seconds since the epoch, in UTC -

   326 such as that outputted by ``time.time()``. If set to ``None``, defaults to the current

   327 time.

   328 

   329 Outputs a string in the format ``Wdy, DD-Mon-YYYY HH:MM:SS GMT``.

   330 

   331 .. function:: http_date(epoch_seconds=None)

   332 

   333 Formats the time to match the RFC 1123 date format as specified by HTTP

   334 `RFC 2616`_ section 3.3.1.

   335 

   336 .. _RFC 2616: http://www.w3.org/Protocols/rfc2616/rfc2616.txt

   337 

   338 Accepts a floating point number expressed in seconds since the epoch, in UTC -

   339 such as that outputted by ``time.time()``. If set to ``None``, defaults to the current

   340 time.

   341 

   342 Outputs a string in the format ``Wdy, DD Mon YYYY HH:MM:SS GMT``.

   343 

   344 .. function:: base36_to_int(s)

   345 

   346 Converted a base 36 string to an integer

   347 

   348 .. function:: int_to_base36(i)

   349 

   350 Converts an integer to a base36 string

   351 

   352 ``django.utils.safestring``

   353 ===========================

   354 

   355 .. module:: django.utils.safestring

   356    :synopsis: Functions and classes for working with strings that can be displayed safely without further escaping in HTML.

   357 

   358 Functions and classes for working with "safe strings": strings that can be

   359 displayed safely without further escaping in HTML. Marking something as a "safe

   360 string" means that the producer of the string has already turned characters

   361 that should not be interpreted by the HTML engine (e.g. '<') into the

   362 appropriate entities.

   363 

   364 .. class:: SafeString

   365 

   366 A string subclass that has been specifically marked as "safe" (requires no

   367 further escaping) for HTML output purposes.

   368 

   369 .. class:: SafeUnicode

   370 

   371 A unicode subclass that has been specifically marked as "safe" for HTML output

   372 purposes.

   373 

   374 .. function:: mark_safe(s)

   375 

   376 Explicitly mark a string as safe for (HTML) output purposes. The returned

   377 object can be used everywhere a string or unicode object is appropriate.

   378 

   379 Can be called multiple times on a single string.

   380 

   381 .. function:: mark_for_escaping(s)

   382 

   383 Explicitly mark a string as requiring HTML escaping upon output. Has no effect

   384 on ``SafeData`` subclasses.

   385 

   386 Can be called multiple times on a single string (the resulting escaping is only

   387 applied once).

   388 

   389 ``django.utils.translation``

   390 ============================

   391 

   392 .. module:: django.utils.translation

   393    :synopsis: Internationalization support.

   394 

   395 For a complete discussion on the usage of the following see the

   396 :doc:`Internationalization documentation </topics/i18n/internationalization>`.

   397 

   398 .. function:: gettext(message)

   399 

   400 Translates ``message`` and returns it in a UTF-8 bytestring

   401 

   402 .. function:: ugettext(message)

   403 

   404 Translates ``message`` and returns it in a unicode string

   405 

   406 .. function:: gettext_lazy(message)

   407 .. function:: ugettext_lazy(message)

   408 

   409 Same as the non-lazy versions above, but using lazy execution.

   410 

   411 See :ref:`lazy translations documentation <lazy-translations>`.

   412 

   413 .. function:: gettext_noop(message)

   414 

   415 Marks strings for translation but doesn't translate them now. This can be used

   416 to store strings in global variables that should stay in the base language

   417 (because they might be used externally) and will be translated later.

   418 

   419 .. function:: ngettext(singular, plural, number)

   420 

   421 Translates ``singular`` and ``plural`` and returns the appropriate string

   422 based on ``number`` in a UTF-8 bytestring

   423 

   424 .. function:: ungettext(singular, plural, number)

   425 

   426 Translates ``singular`` and ``plural`` and returns the appropriate string based

   427 on ``number`` in a unicode string

   428 

   429 .. function:: ngettext_lazy(singular, plural, number)

   430 .. function:: ungettext_lazy(singular, plural, number)

   431 

   432 Same as the non-lazy versions above, but using lazy execution.

   433 

   434 See :ref:`lazy translations documentation <lazy-translations>`.

   435 

   436 .. function:: string_concat(*strings)

   437 

   438 Lazy variant of string concatenation, needed for translations that are

   439 constructed from multiple parts.

   440 

   441 .. function:: activate(language)

   442 

   443 Fetches the translation object for a given tuple of application name and

   444 language and installs it as the current translation object for the current

   445 thread.

   446 

   447 .. function:: deactivate()

   448 

   449 De-installs the currently active translation object so that further _ calls will

   450 resolve against the default translation object, again.

   451 

   452 .. function:: deactivate_all()

   453 

   454 Makes the active translation object a NullTranslations() instance. This is

   455 useful when we want delayed translations to appear as the original string for

   456 some reason.

   457 

   458 .. function:: get_language()

   459 

   460 Returns the currently selected language code.

   461 

   462 .. function:: get_language_bidi()

   463 

   464 Returns selected language's BiDi layout:

   465 

   466  * ``False`` = left-to-right layout

   467  * ``True`` = right-to-left layout

   468 

   469 .. function:: get_date_formats()

   470 

   471 Checks whether translation files provide a translation for some technical

   472 message ID to store date and time formats. If it doesn't contain one, the

   473 formats provided in the settings will be used.

   474 

   475 .. function:: get_language_from_request(request)

   476 

   477 Analyzes the request to find what language the user wants the system to show.

   478 Only languages listed in settings.LANGUAGES are taken into account. If the user

   479 requests a sublanguage where we have a main language, we send out the main

   480 language.

   481 

   482 .. function:: to_locale(language)

   483 

   484 Turns a language name (en-us) into a locale name (en_US).

   485 

   486 .. function:: templatize(src)

   487 

   488 Turns a Django template into something that is understood by xgettext. It does

   489 so by translating the Django translation tags into standard gettext function

   490 invocations.

   491 

   492 ``django.utils.tzinfo``

   493 =======================

   494 

   495 .. module:: django.utils.tzinfo

   496    :synopsis: Implementation of ``tzinfo`` classes for use with ``datetime.datetime``.

   497 

   498 .. class:: FixedOffset

   499 

   500 Fixed offset in minutes east from UTC.

   501 

   502 .. class:: LocalTimezone

   503 

   504 Proxy timezone information from time module.