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<a class="github" href="urlpatterns.py"></a>
# Format suffixes
> Section 6.2.1 does not say that content negotiation should be
used all the time.
>
> — Roy Fielding, [REST discuss mailing list][cite]
A common pattern for Web APIs is to use filename extensions on URLs to provide an endpoint for a given media type. For example, 'http://example.com/api/users.json' to serve a JSON representation.
Adding format-suffix patterns to each individual entry in the URLconf for your API is error-prone and non-DRY, so REST framework provides a shortcut to adding these patterns to your URLConf.
## format_suffix_patterns
**Signature**: format_suffix_patterns(urlpatterns, suffix_required=False, allowed=None)
Returns a URL pattern list which includes format suffix patterns appended to each of the URL patterns provided.
Arguments:
* **urlpatterns**: Required. A URL pattern list.
* **suffix_required**: Optional. A boolean indicating if suffixes in the URLs should be optional or mandatory. Defaults to `False`, meaning that suffixes are optional by default.
* **allowed**: Optional. A list or tuple of valid format suffixes. If not provided, a wildcard format suffix pattern will be used.
Example:
from rest_framework.urlpatterns import format_suffix_patterns
urlpatterns = patterns('blog.views',
url(r'^/$', 'api_root'),
url(r'^comments/$', 'comment_list'),
url(r'^comments/(?P<pk>[0-9]+)/$', 'comment_detail')
)
urlpatterns = format_suffix_patterns(urlpatterns, allowed=['json', 'html'])
When using `format_suffix_patterns`, you must make sure to add the `'format'` keyword argument to the corresponding views. For example:
@api_view(('GET', 'POST'))
def comment_list(request, format=None):
# do stuff...
Or with class based views:
class CommentList(APIView):
def get(self, request, format=None):
# do stuff...
def post(self, request, format=None):
# do stuff...
The name of the kwarg used may be modified by using the `FORMAT_SUFFIX_KWARG` setting.
Also note that `format_suffix_patterns` does not support descending into `include` URL patterns.
---
## Accept headers vs. format suffixes
There seems to be a view among some of the Web community that filename extensions are not a RESTful pattern, and that `HTTP Accept` headers should always be used instead.
It is actually a misconception. For example, take the following quote from Roy Fielding discussing the relative merits of query parameter media-type indicators vs. file extension media-type indicators:
“That's why I always prefer extensions. Neither choice has anything to do with REST.” — Roy Fielding, [REST discuss mailing list][cite2]
The quote does not mention Accept headers, but it does make it clear that format suffixes should be considered an acceptable pattern.
[cite]: http://tech.groups.yahoo.com/group/rest-discuss/message/5857
[cite2]: http://tech.groups.yahoo.com/group/rest-discuss/message/14844
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