Django comes with a high-level syndication-feed-generating framework that makes creating RSS and Atom feeds easy.
To create any syndication feed, all you have to do is write a short Python class. You can create as many feeds as you want.
Django also comes with a lower-level feed-generating API. Use this if you want to generate feeds outside of a Web context, or in some other lower-level way.
The high-level feed-generating framework is a view that’s hooked to /feeds/ by default. Django uses the remainder of the URL (everything after /feeds/) to determine which feed to output.
To create a feed, just write a Feed class and point to it in your URLconf.
To activate syndication feeds on your Django site, add this line to your URLconf:
(r'^feeds/(?P<url>.*)/$', 'django.contrib.syndication.views.feed', {'feed_dict': feeds}),
This tells Django to use the RSS framework to handle all URLs starting with "feeds/". (You can change that "feeds/" prefix to fit your own needs.)
This URLconf line has an extra argument: {'feed_dict': feeds}. Use this extra argument to pass the syndication framework the feeds that should be published under that URL.
Specifically, feed_dict should be a dictionary that maps a feed's slug (short URL label) to its Feed class.
You can define the feed_dict in the URLconf itself. Here's a full example URLconf:
from django.conf.urls.defaults import *
from myproject.feeds import LatestEntries, LatestEntriesByCategory
feeds = {
'latest': LatestEntries,
'categories': LatestEntriesByCategory,
}
urlpatterns = patterns('',
# ...
(r'^feeds/(?P<url>.*)/$', 'django.contrib.syndication.views.feed',
{'feed_dict': feeds}),
# ...
)
The above example registers two feeds:
Once that's set up, you just need to define the Feed classes themselves.
A Feed class is a simple Python class that represents a syndication feed. A feed can be simple (e.g., a "site news" feed, or a basic feed displaying the latest entries of a blog) or more complex (e.g., a feed displaying all the blog entries in a particular category, where the category is variable).
Feed classes must subclass django.contrib.syndication.feeds.Feed. They can live anywhere in your codebase.
This simple example, taken from chicagocrime.org, describes a feed of the latest five news items:
from django.contrib.syndication.feeds import Feed
from chicagocrime.models import NewsItem
class LatestEntries(Feed):
title = "Chicagocrime.org site news"
link = "/sitenews/"
description = "Updates on changes and additions to chicagocrime.org."
def items(self):
return NewsItem.objects.order_by('-pub_date')[:5]
Note:
One thing's left to do. In an RSS feed, each <item> has a <title>, <link> and <description>. We need to tell the framework what data to put into those elements.
To specify the contents of <title> and <description>, create Django templates called feeds/latest_title.html and feeds/latest_description.html, where latest is the slug specified in the URLconf for the given feed. Note the .html extension is required. The RSS system renders that template for each item, passing it two template context variables:
If you don't create a template for either the title or description, the framework will use the template "{{ obj }}" by default -- that is, the normal string representation of the object. You can also change the names of these two templates by specifying title_template and description_template as attributes of your Feed class.
To specify the contents of <link>, you have two options. For each item in items(), Django first tries calling a method item_link() in the Feed class, passing it a single parameter, item, which is the object itself. If that method doesn't exist, Django tries executing a get_absolute_url() method on that object. . Both get_absolute_url() and item_link() should return the item's URL as a normal Python string. As with get_absolute_url(), the result of item_link() will be included directly in the URL, so you are responsible for doing all necessary URL quoting and conversion to ASCII inside the method itself.
For the LatestEntries example above, we could have very simple feed templates:
latest_title.html:
{{ obj.title }}
latest_description.html:
{{ obj.description }}
The framework also supports more complex feeds, via parameters.
For example, chicagocrime.org offers an RSS feed of recent crimes for every police beat in Chicago. It'd be silly to create a separate Feed class for each police beat; that would violate the DRY principle and would couple data to programming logic. Instead, the syndication framework lets you make generic feeds that output items based on information in the feed's URL.
On chicagocrime.org, the police-beat feeds are accessible via URLs like this:
The slug here is "beats". The syndication framework sees the extra URL bits after the slug -- 0613 and 1424 -- and gives you a hook to tell it what those URL bits mean, and how they should influence which items get published in the feed.
An example makes this clear. Here's the code for these beat-specific feeds:
from django.contrib.syndication.feeds import FeedDoesNotExist
from django.core.exceptions import ObjectDoesNotExist
class BeatFeed(Feed):
def get_object(self, bits):
# In case of "/rss/beats/0613/foo/bar/baz/", or other such clutter,
# check that bits has only one member.
if len(bits) != 1:
raise ObjectDoesNotExist
return Beat.objects.get(beat__exact=bits[0])
def title(self, obj):
return "Chicagocrime.org: Crimes for beat %s" % obj.beat
def link(self, obj):
if not obj:
raise FeedDoesNotExist
return obj.get_absolute_url()
def description(self, obj):
return "Crimes recently reported in police beat %s" % obj.beat
def items(self, obj):
return Crime.objects.filter(beat__id__exact=obj.id).order_by('-crime_date')[:30]
Here's the basic algorithm the RSS framework follows, given this class and a request to the URL /rss/beats/0613/:
The framework gets the URL /rss/beats/0613/ and notices there's an extra bit of URL after the slug. It splits that remaining string by the slash character ("/") and calls the Feed class' get_object() method, passing it the bits. In this case, bits is ['0613']. For a request to /rss/beats/0613/foo/bar/, bits would be ['0613', 'foo', 'bar'].
get_object() is responsible for retrieving the given beat, from the given bits. In this case, it uses the Django database API to retrieve the beat. Note that get_object() should raise django.core.exceptions.ObjectDoesNotExist if given invalid parameters. There's no try/except around the Beat.objects.get() call, because it's not necessary; that function raises Beat.DoesNotExist on failure, and Beat.DoesNotExist is a subclass of ObjectDoesNotExist. Raising ObjectDoesNotExist in get_object() tells Django to produce a 404 error for that request.
The get_object() method also has a chance to handle the /rss/beats/ url. In this case, bits will be an empty list. In our example, len(bits) != 1 and an ObjectDoesNotExist exception will be raised, so /rss/beats/ will generate a 404 page. But you can handle this case however you like. For example, you could generate a combined feed for all beats.
To generate the feed's <title>, <link> and <description>, Django uses the title(), link() and description() methods. In the previous example, they were simple string class attributes, but this example illustrates that they can be either strings or methods. For each of title, link and description, Django follows this algorithm:
Inside the link() method, we handle the possibility that obj might be None, which can occur when the URL isn't fully specified. In some cases, you might want to do something else in this case, which would mean you'd need to check for obj existing in other methods as well. (The link() method is called very early in the feed generation process, so it's a good place to bail out early.)
Finally, note that items() in this example also takes the obj argument. The algorithm for items is the same as described in the previous step -- first, it tries items(obj)(), then items(), then finally an items class attribute (which should be a list).
The ExampleFeed class below gives full documentation on methods and attributes of Feed classes.
By default, feeds produced in this framework use RSS 2.0.
To change that, add a feed_type attribute to your Feed class, like so:
from django.utils.feedgenerator import Atom1Feed
class MyFeed(Feed):
feed_type = Atom1Feed
Note that you set feed_type to a class object, not an instance.
Currently available feed types are:
To specify enclosures, such as those used in creating podcast feeds, use the item_enclosure_url, item_enclosure_length and item_enclosure_mime_type hooks. See the ExampleFeed class below for usage examples.
Feeds created by the syndication framework automatically include the appropriate <language> tag (RSS 2.0) or xml:lang attribute (Atom). This comes directly from your LANGUAGE_CODE setting.
The link method/attribute can return either an absolute URL (e.g. "/blog/") or a URL with the fully-qualified domain and protocol (e.g. "http://www.example.com/blog/"). If link doesn't return the domain, the syndication framework will insert the domain of the current site, according to your SITE_ID setting.
Atom feeds require a <link rel="self"> that defines the feed's current location. The syndication framework populates this automatically, using the domain of the current site according to the SITE_ID setting.
Some developers like to make available both Atom and RSS versions of their feeds. That's easy to do with Django: Just create a subclass of your Feed class and set the feed_type to something different. Then update your URLconf to add the extra versions.
Here's a full example:
from django.contrib.syndication.feeds import Feed
from chicagocrime.models import NewsItem
from django.utils.feedgenerator import Atom1Feed
class RssSiteNewsFeed(Feed):
title = "Chicagocrime.org site news"
link = "/sitenews/"
description = "Updates on changes and additions to chicagocrime.org."
def items(self):
return NewsItem.objects.order_by('-pub_date')[:5]
class AtomSiteNewsFeed(RssSiteNewsFeed):
feed_type = Atom1Feed
subtitle = RssSiteNewsFeed.description
Note
In this example, the RSS feed uses a description while the Atom feed uses a subtitle. That's because Atom feeds don't provide for a feed-level "description," but they do provide for a "subtitle."
If you provide a description in your Feed class, Django will not automatically put that into the subtitle element, because a subtitle and description are not necessarily the same thing. Instead, you should define a subtitle attribute.
In the above example, we simply set the Atom feed's subtitle to the RSS feed's description, because it's quite short already.
And the accompanying URLconf:
from django.conf.urls.defaults import *
from myproject.feeds import RssSiteNewsFeed, AtomSiteNewsFeed
feeds = {
'rss': RssSiteNewsFeed,
'atom': AtomSiteNewsFeed,
}
urlpatterns = patterns('',
# ...
(r'^feeds/(?P<url>.*)/$', 'django.contrib.syndication.views.feed',
{'feed_dict': feeds}),
# ...
)
This example illustrates all possible attributes and methods for a Feed class:
from django.contrib.syndication.feeds import Feed
from django.utils import feedgenerator
class ExampleFeed(Feed):
# FEED TYPE -- Optional. This should be a class that subclasses
# django.utils.feedgenerator.SyndicationFeed. This designates which
# type of feed this should be: RSS 2.0, Atom 1.0, etc.
# If you don't specify feed_type, your feed will be RSS 2.0.
# This should be a class, not an instance of the class.
feed_type = feedgenerator.Rss201rev2Feed
# TEMPLATE NAMES -- Optional. These should be strings representing
# names of Django templates that the system should use in rendering the
# title and description of your feed items. Both are optional.
# If you don't specify one, or either, Django will use the template
# 'feeds/SLUG_title.html' and 'feeds/SLUG_description.html', where SLUG
# is the slug you specify in the URL.
title_template = None
description_template = None
# TITLE -- One of the following three is required. The framework looks
# for them in this order.
def title(self, obj):
"""
Takes the object returned by get_object() and returns the feed's
title as a normal Python string.
"""
def title(self):
"""
Returns the feed's title as a normal Python string.
"""
title = 'foo' # Hard-coded title.
# LINK -- One of the following three is required. The framework looks
# for them in this order.
def link(self, obj):
"""
Takes the object returned by get_object() and returns the feed's
link as a normal Python string.
"""
def link(self):
"""
Returns the feed's link as a normal Python string.
"""
link = '/foo/bar/' # Hard-coded link.
# GUID -- One of the following three is optional. The framework looks
# for them in this order. This property is only used for Atom feeds
# (where it is the feed-level ID element). If not provided, the feed
# link is used as the ID.
def feed_guid(self, obj):
"""
Takes the object returned by get_object() and returns the globally
unique ID for the feed as a normal Python string.
"""
def feed_guid(self):
"""
Returns the feed's globally unique ID as a normal Python string.
"""
feed_guid = '/foo/bar/1234' # Hard-coded guid.
# DESCRIPTION -- One of the following three is required. The framework
# looks for them in this order.
def description(self, obj):
"""
Takes the object returned by get_object() and returns the feed's
description as a normal Python string.
"""
def description(self):
"""
Returns the feed's description as a normal Python string.
"""
description = 'Foo bar baz.' # Hard-coded description.
# AUTHOR NAME --One of the following three is optional. The framework
# looks for them in this order.
def author_name(self, obj):
"""
Takes the object returned by get_object() and returns the feed's
author's name as a normal Python string.
"""
def author_name(self):
"""
Returns the feed's author's name as a normal Python string.
"""
author_name = 'Sally Smith' # Hard-coded author name.
# AUTHOR E-MAIL --One of the following three is optional. The framework
# looks for them in this order.
def author_email(self, obj):
"""
Takes the object returned by get_object() and returns the feed's
author's e-mail as a normal Python string.
"""
def author_email(self):
"""
Returns the feed's author's e-mail as a normal Python string.
"""
author_email = 'test@example.com' # Hard-coded author e-mail.
# AUTHOR LINK --One of the following three is optional. The framework
# looks for them in this order. In each case, the URL should include
# the "http://" and domain name.
def author_link(self, obj):
"""
Takes the object returned by get_object() and returns the feed's
author's URL as a normal Python string.
"""
def author_link(self):
"""
Returns the feed's author's URL as a normal Python string.
"""
author_link = 'http://www.example.com/' # Hard-coded author URL.
# CATEGORIES -- One of the following three is optional. The framework
# looks for them in this order. In each case, the method/attribute
# should return an iterable object that returns strings.
def categories(self, obj):
"""
Takes the object returned by get_object() and returns the feed's
categories as iterable over strings.
"""
def categories(self):
"""
Returns the feed's categories as iterable over strings.
"""
categories = ("python", "django") # Hard-coded list of categories.
# COPYRIGHT NOTICE -- One of the following three is optional. The
# framework looks for them in this order.
def copyright(self, obj):
"""
Takes the object returned by get_object() and returns the feed's
copyright notice as a normal Python string.
"""
def copyright(self):
"""
Returns the feed's copyright notice as a normal Python string.
"""
copyright = 'Copyright (c) 2007, Sally Smith' # Hard-coded copyright notice.
# TTL -- One of the following three is optional. The framework looks
# for them in this order. Ignored for Atom feeds.
def ttl(self, obj):
"""
Takes the object returned by get_object() and returns the feed's
TTL (Time To Live) as a normal Python string.
"""
def ttl(self):
"""
Returns the feed's TTL as a normal Python string.
"""
ttl = 600 # Hard-coded Time To Live.
# ITEMS -- One of the following three is required. The framework looks
# for them in this order.
def items(self, obj):
"""
Takes the object returned by get_object() and returns a list of
items to publish in this feed.
"""
def items(self):
"""
Returns a list of items to publish in this feed.
"""
items = ('Item 1', 'Item 2') # Hard-coded items.
# GET_OBJECT -- This is required for feeds that publish different data
# for different URL parameters. (See "A complex example" above.)
def get_object(self, bits):
"""
Takes a list of strings gleaned from the URL and returns an object
represented by this feed. Raises
django.core.exceptions.ObjectDoesNotExist on error.
"""
# ITEM LINK -- One of these three is required. The framework looks for
# them in this order.
# First, the framework tries the two methods below, in
# order. Failing that, it falls back to the get_absolute_url()
# method on each item returned by items().
def item_link(self, item):
"""
Takes an item, as returned by items(), and returns the item's URL.
"""
def item_link(self):
"""
Returns the URL for every item in the feed.
"""
# ITEM_GUID -- The following method is optional. If not provided, the
# item's link is used by default.
def item_guid(self, obj):
"""
Takes an item, as return by items(), and returns the item's ID.
"""
# ITEM AUTHOR NAME -- One of the following three is optional. The
# framework looks for them in this order.
def item_author_name(self, item):
"""
Takes an item, as returned by items(), and returns the item's
author's name as a normal Python string.
"""
def item_author_name(self):
"""
Returns the author name for every item in the feed.
"""
item_author_name = 'Sally Smith' # Hard-coded author name.
# ITEM AUTHOR E-MAIL --One of the following three is optional. The
# framework looks for them in this order.
#
# If you specify this, you must specify item_author_name.
def item_author_email(self, obj):
"""
Takes an item, as returned by items(), and returns the item's
author's e-mail as a normal Python string.
"""
def item_author_email(self):
"""
Returns the author e-mail for every item in the feed.
"""
item_author_email = 'test@example.com' # Hard-coded author e-mail.
# ITEM AUTHOR LINK --One of the following three is optional. The
# framework looks for them in this order. In each case, the URL should
# include the "http://" and domain name.
#
# If you specify this, you must specify item_author_name.
def item_author_link(self, obj):
"""
Takes an item, as returned by items(), and returns the item's
author's URL as a normal Python string.
"""
def item_author_link(self):
"""
Returns the author URL for every item in the feed.
"""
item_author_link = 'http://www.example.com/' # Hard-coded author URL.
# ITEM ENCLOSURE URL -- One of these three is required if you're
# publishing enclosures. The framework looks for them in this order.
def item_enclosure_url(self, item):
"""
Takes an item, as returned by items(), and returns the item's
enclosure URL.
"""
def item_enclosure_url(self):
"""
Returns the enclosure URL for every item in the feed.
"""
item_enclosure_url = "/foo/bar.mp3" # Hard-coded enclosure link.
# ITEM ENCLOSURE LENGTH -- One of these three is required if you're
# publishing enclosures. The framework looks for them in this order.
# In each case, the returned value should be either an integer, or a
# string representation of the integer, in bytes.
def item_enclosure_length(self, item):
"""
Takes an item, as returned by items(), and returns the item's
enclosure length.
"""
def item_enclosure_length(self):
"""
Returns the enclosure length for every item in the feed.
"""
item_enclosure_length = 32000 # Hard-coded enclosure length.
# ITEM ENCLOSURE MIME TYPE -- One of these three is required if you're
# publishing enclosures. The framework looks for them in this order.
def item_enclosure_mime_type(self, item):
"""
Takes an item, as returned by items(), and returns the item's
enclosure MIME type.
"""
def item_enclosure_mime_type(self):
"""
Returns the enclosure MIME type for every item in the feed.
"""
item_enclosure_mime_type = "audio/mpeg" # Hard-coded enclosure MIME type.
# ITEM PUBDATE -- It's optional to use one of these three. This is a
# hook that specifies how to get the pubdate for a given item.
# In each case, the method/attribute should return a Python
# datetime.datetime object.
def item_pubdate(self, item):
"""
Takes an item, as returned by items(), and returns the item's
pubdate.
"""
def item_pubdate(self):
"""
Returns the pubdate for every item in the feed.
"""
item_pubdate = datetime.datetime(2005, 5, 3) # Hard-coded pubdate.
# ITEM CATEGORIES -- It's optional to use one of these three. This is
# a hook that specifies how to get the list of categories for a given
# item. In each case, the method/attribute should return an iterable
# object that returns strings.
def item_categories(self, item):
"""
Takes an item, as returned by items(), and returns the item's
categories.
"""
def item_categories(self):
"""
Returns the categories for every item in the feed.
"""
item_categories = ("python", "django") # Hard-coded categories.
# ITEM COPYRIGHT NOTICE (only applicable to Atom feeds) -- One of the
# following three is optional. The framework looks for them in this
# order.
def item_copyright(self, obj):
"""
Takes an item, as returned by items(), and returns the item's
copyright notice as a normal Python string.
"""
def item_copyright(self):
"""
Returns the copyright notice for every item in the feed.
"""
item_copyright = 'Copyright (c) 2007, Sally Smith' # Hard-coded copyright notice.
Behind the scenes, the high-level RSS framework uses a lower-level framework for generating feeds' XML. This framework lives in a single module: django/utils/feedgenerator.py.
You use this framework on your own, for lower-level feed generation. You can also create custom feed generator subclasses for use with the feed_type Feed option.
The feedgenerator module contains a base class:
and several subclasses:
Each of these three classes knows how to render a certain type of feed as XML. They share this interface:
Initialize the feed with the given dictionary of metadata, which applies to the entire feed. Required keyword arguments are:
There's also a bunch of other optional keywords:
Any extra keyword arguments you pass to __init__ will be stored in self.feed for use with custom feed generators.
All parameters should be Unicode objects, except categories, which should be a sequence of Unicode objects.
Add an item to the feed with the given parameters.
Required keyword arguments are:
Optional keyword arguments are:
Extra keyword arguments will be stored for custom feed generators.
All parameters, if given, should be Unicode objects, except:
For example, to create an Atom 1.0 feed and print it to standard output:
>>> from django.utils import feedgenerator
>>> f = feedgenerator.Atom1Feed(
... title=u"My Weblog",
... link=u"http://www.example.com/",
... description=u"In which I write about what I ate today.",
... language=u"en")
>>> f.add_item(title=u"Hot dog today",
... link=u"http://www.example.com/entries/1/",
... description=u"<p>Today I had a Vienna Beef hot dog. It was pink, plump and perfect.</p>")
>>> print f.writeString('UTF-8')
<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xml:lang="en">
...
</feed>
If you need to produce a custom feed format, you've got a couple of options.
If the feed format is totally custom, you'll want to subclass SyndicationFeed and completely replace the write() and writeString() methods.
However, if the feed format is a spin-off of RSS or Atom (i.e. GeoRSS, Apple's iTunes podcast format, etc.), you've got a better choice. These types of feeds typically add extra elements and/or attributes to the underlying format, and there are a set of methods that SyndicationFeed calls to get these extra attributes. Thus, you can subclass the appropriate feed generator class (Atom1Feed or Rss201rev2Feed) and extend these callbacks. They are:
Warning
If you override any of these methods, be sure to call the superclass methods since they add the required elements for each feed format.
For example, you might start implementing an iTunes RSS feed generator like so:
class iTunesFeed(Rss201rev2Feed):
def root_attributes(self):
attrs = super(iTunesFeed, self).root_attributes()
attrs['xmlns:itunes'] = 'http://www.itunes.com/dtds/podcast-1.0.dtd'
return attrs
def add_root_elements(self, handler):
super(iTunesFeed, self).add_root_elements(handler)
handler.addQuickElement('itunes:explicit', 'clean')
Obviously there's a lot more work to be done for a complete custom feed class, but the above example should demonstrate the basic idea.
Sep 20, 2009