Django Utils¶
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 internal release deprecation policy.
django.utils.cache
¶
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, internationalization middleware would need
to distinguish caches by the Accept-language
header.
-
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
(exactlyTrue
, 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.
-
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).
-
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. TheCACHE_MIDDLEWARE_SECONDS
setting is used by default.
-
add_never_cache_headers
(response)¶ Adds headers to a response to indicate that a page should never be cached.
-
patch_vary_headers
(response, newheaders)¶ Adds (or updates) the
Vary
header in the givenHttpResponse
object.newheaders
is a list of header names that should be inVary
. Existing headers inVary
aren’t removed.
-
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
.
-
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
¶
-
class
SortedDict
¶ The
django.utils.datastructures.SortedDict
class is a dictionary that keeps its keys in the order in which they’re inserted.SortedDict
adds two additional methods to the standard Pythondict
class:-
insert
(index, key, value)¶ Deprecated since version 1.5.
Inserts the key, value pair before the item with the given index.
-
value_for_index
(index)¶ Deprecated since version 1.5.
Returns the value of the item at the given zero-based index.
-
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
¶
The functions defined in this module share the following properties:
- They raise
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.
-
parse_date
(value)¶ Parses a string and returns a
datetime.date
.
-
parse_time
(value)¶ Parses a string and returns a
datetime.time
.UTC offsets aren’t supported; if
value
describes one, the result isNone
.
-
parse_datetime
(value)¶ Parses a string and returns a
datetime.datetime
.UTC offsets are supported; if
value
describes one, the result’stzinfo
attribute is aFixedOffset
instance.
django.utils.decorators
¶
-
method_decorator
(decorator)¶ Converts a function decorator into a method decorator. See decorating class based views for example usage.
-
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.
-
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, thecache_page()
decorator is created from theCacheMiddleware
like this:cache_page = decorator_from_middleware_with_args(CacheMiddleware) @cache_page(3600) def my_view(request): pass
django.utils.encoding
¶
-
class
StrAndUnicode
¶ A class that derives
__str__
from__unicode__
.On Python 2,
__str__
returns the output of__unicode__
encoded as a UTF-8 bytestring. On Python 3,__str__
returns the output of__unicode__
.Useful as a mix-in. If you support Python 2 and 3 with a single code base, you can inherit this mix-in and just define
__unicode__
.
-
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.
-
smart_text
(s, encoding='utf-8', strings_only=False, errors='strict')¶ Returns a text object representing
s
–unicode
on Python 2 andstr
on Python 3. Treats bytestrings using theencoding
codec.If
strings_only
isTrue
, don’t convert (some) non-string-like objects.
-
smart_unicode
(s, encoding='utf-8', strings_only=False, errors='strict')¶ Historical name of
smart_text()
. Only available under Python 2.
-
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)
.
-
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
isTrue
, don’t convert (some) non-string-like objects.
-
force_unicode
(s, encoding='utf-8', strings_only=False, errors='strict')¶ Historical name of
force_text()
. Only available under Python 2.
-
smart_bytes
(s, encoding='utf-8', strings_only=False, errors='strict')¶ Returns a bytestring version of
s
, encoded as specified inencoding
.If
strings_only
isTrue
, don’t convert (some) non-string-like objects.
-
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
isTrue
, don’t convert (some) non-string-like objects.
-
smart_str
(s, encoding='utf-8', strings_only=False, errors='strict')¶ Alias of
smart_bytes()
on Python 2 andsmart_text()
on Python 3. This function returns astr
or a lazy string.For instance, this is suitable for writing to
sys.stdout
on Python 2 and 3.
-
force_str
(s, encoding='utf-8', strings_only=False, errors='strict')¶ Alias of
force_bytes()
on Python 2 andforce_text()
on Python 3. This function always returns astr
.
-
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.
-
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
¶
Sample usage:
>>> from django.utils import feedgenerator
>>> feed = feedgenerator.Rss201rev2Feed(
... title=u"Poynter E-Media Tidbits",
... link=u"http://www.poynter.org/column.asp?id=31",
... description=u"A group Weblog by the sharpest minds in online media/journalism/publishing.",
... language=u"en",
... )
>>> feed.add_item(
... title="Hello",
... link=u"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
-
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().
-
__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 inself.feed
.All parameters should be Unicode objects, except
categories
, which should be a sequence of Unicode objects.
-
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])¶ Adds an item to the feed. All args are expected to be Python
unicode
objects exceptpubdate
, which is adatetime.datetime
object, andenclosure
, which is an instance of theEnclosure
class.
-
num_items
()¶
-
root_attributes
()¶ Return extra attributes to place on the root (i.e. feed/channel) element. Called from
write()
.
-
add_root_elements
(handler)¶ Add elements in the root (i.e. feed/channel) element. Called from
write()
.
-
item_attributes
(item)¶ Return extra attributes to place on each item (i.e. item/entry) element.
-
add_item_elements
(handler, item)¶ Add elements on each item (i.e. item/entry) element.
-
write
(outfile, encoding)¶ Outputs the feed in the given encoding to
outfile
, which is a file-like object. Subclasses should override this.
-
writeString
(encoding)¶ Returns the feed in the given encoding as a string.
-
latest_post_date
()¶ Returns the latest item’s
pubdate
. If none of them have apubdate
, this returns the current date/time.
-
Atom1Feed¶
-
class
Atom1Feed
(SyndicationFeed)¶ Spec: http://www.atomenabled.org/developers/syndication/atom-format-spec.php
django.utils.functional
¶
-
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 the first argument, 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' ... 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 includeunicode
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
¶
Usually you should build up HTML using Django’s templates to make use of its
autoescape mechanism, using the utilities in django.utils.safestring
where appropriate. This module provides some additional low level utilitiesfor
escaping HTML.
-
escape
(text)¶ Returns the given text with ampersands, quotes and angle brackets encoded for use in HTML. The input is first passed through
force_text()
and the output hasmark_safe()
applied.
-
conditional_escape
(text)¶ Similar to
escape()
, except that it doesn’t operate on pre-escaped strings, so it will not double escape.
-
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
conditional_escape()
before being passed tostr.format
.For the case of building up small HTML fragments, this function is to be preferred over string interpolation using
%
orstr.format
directly, because it applies escaping to all arguments - just like the Template system applies escaping by default.So, instead of writing:
mark_safe(u"%s <b>%s</b> %s" % (some_html, escape(some_text), escape(some_other_text), ))
you should instead use:
format_html(u"%{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
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 throughconditional_escape()
which (ultimately) callsforce_text()
on the values.
-
format_html_join
(sep, format_string, args_generator)¶ A wrapper of
format_html()
, for the common case of a group of arguments that need to be formatted using the same format string, and then joined usingsep
.sep
is also passed throughconditional_escape()
.args_generator
should be an iterator that returns the sequence ofargs
that will be passed toformat_html()
. For example:format_html_join('\n', "<li>{0} {1}</li>", ((u.first_name, u.last_name) for u in users))
Removes anything that looks like an html tag from the string, that is anything contained within
<>
.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"
.
Removes a 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"
.
django.utils.http
¶
-
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 subsequentiri_to_uri()
call without double-quoting occurring. Employs lazy execution.
-
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.
-
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.
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 toNone
, defaults to the current time.Outputs a string in the format
Wdy, DD-Mon-YYYY HH:MM:SS GMT
.
-
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 toNone
, defaults to the current time.Outputs a string in the format
Wdy, DD Mon YYYY HH:MM:SS GMT
.
-
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 along
.
-
int_to_base36
(i)¶ Converts a positive integer to a base 36 string. On Python 2
i
must be smaller thansys.maxint
.
django.utils.safestring
¶
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 isSafeBytes
on Python 2 andSafeText
on Python 3.
-
class
SafeText
¶ A
str
(in Python 3) orunicode
(in Python 2) subclass that has been specifically marked as “safe” for HTML output purposes.
-
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.
-
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
¶
-
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
¶
For a complete discussion on the usage of the following see the translation documentation.
-
gettext
(message)¶ Translates
message
and returns it in a UTF-8 bytestring
-
ugettext
(message)¶ Translates
message
and returns it in a unicode string
-
pgettext
(context, message)¶ Translates
message
given thecontext
and returns it in a unicode string.For more information, see Contextual markers.
-
gettext_lazy
(message)¶
-
ugettext_lazy
(message)¶
-
pgettext_lazy
(context, message)¶ Same as the non-lazy versions above, but using lazy execution.
-
gettext_noop
(message)¶
-
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.
-
ngettext
(singular, plural, number)¶ Translates
singular
andplural
and returns the appropriate string based onnumber
in a UTF-8 bytestring.
-
ungettext
(singular, plural, number)¶ Translates
singular
andplural
and returns the appropriate string based onnumber
in a unicode string.
-
npgettext
(context, singular, plural, number)¶ Translates
singular
andplural
and returns the appropriate string based onnumber
and thecontext
in a unicode string.
-
ngettext_lazy
(singular, plural, number)¶
-
ungettext_lazy
(singular, plural, number)¶
-
npgettext_lazy
(singular, plural, number)¶ Same as the non-lazy versions above, but using lazy execution.
-
string_concat
(*strings)¶ Lazy variant of string concatenation, needed for translations that are constructed from multiple parts.
-
activate
(language)¶ Fetches the translation object for a given language and installs it as the current translation object for the current thread.
-
deactivate
()¶ De-installs the currently active translation object so that further _ calls will resolve against the default translation object, again.
-
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.
-
override
(language, deactivate=False)¶ A Python context manager that uses
django.utils.translation.activate()
to fetch the translation object for a given language, installing it as the translation object for the current thread and reinstall the previous active language on exit. Optionally it can simply deinstall the temporary translation on exit withdjango.utils.translation.deactivate()
if the deactivate argument is True. If you pass None as the language argument, a NullTranslations() instance is installed while the context is active.
-
get_language
()¶ Returns the currently selected language code.
-
get_language_bidi
()¶ Returns selected language’s BiDi layout:
False
= left-to-right layoutTrue
= right-to-left layout
-
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
isTrue
, the function first checks the requested URL for whether its path begins with a language code listed in theLANGUAGES
setting.
-
to_locale
(language)¶ Turns a language name (en-us) into a locale name (en_US).
-
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.
django.utils.timezone
¶
-
get_default_timezone
()¶ Returns a
tzinfo
instance that represents the default time zone.
-
get_default_timezone_name
()¶ Returns the name of the default time zone.
-
get_current_timezone
()¶ Returns a
tzinfo
instance that represents the current time zone.
-
get_current_timezone_name
()¶ Returns the name of the current time zone.
-
activate
(timezone)¶ Sets the current time zone. The
timezone
argument must be an instance of atzinfo
subclass or, if pytz is available, a time zone name.
-
deactivate
()¶ Unsets the current time zone.
-
override
(timezone)¶ This is a Python context manager that sets the current time zone on entry with
activate()
, and restores the previously active time zone on exit. If thetimezone
argument isNone
, the current time zone is unset on entry withdeactivate()
instead.
-
localtime
(value, timezone=None)¶ Converts an aware
datetime
to a different time zone, by default the current time zone.This function doesn’t work on naive datetimes; use
make_aware()
instead.
-
now
()¶ Returns an aware or naive
datetime
that represents the current point in time whenUSE_TZ
isTrue
orFalse
respectively.
-
is_aware
(value)¶ Returns
True
ifvalue
is aware,False
if it is naive. This function assumes thatvalue
is adatetime
.
-
is_naive
(value)¶ Returns
True
ifvalue
is naive,False
if it is aware. This function assumes thatvalue
is adatetime
.