Django handles a request by routing the incoming URL path to a view function. The view function is responsible for returning a response back to the client making the request. Different URLs are usually handled by different view functions. To route the request to a specific view function, Django looks at your URL configuration (or URLconf for short). The default project template defines the URLconf in
Your URLconf should be a python module that defines an attribute named
urlpatterns, which is a list of
django.conf.urls.url() instances. Each
url() instance must at minimum define a regular expression (a regex) to match against the URL, and a target, which is either a view function or a different URLconf. If a URL pattern targets a view function, it is a good idea to give it a name to easily reference the pattern later on.
Let's take a look at a basic example:
# In <myproject>/urls.py from django.conf.urls import url from myapp.views import home, about, blog_detail urlpatterns = [ url(r'^$', home, name='home'), url(r'^about/$', about, name='about'), url(r'^blog/(?P<id>\d+)/$', blog_detail, name='blog-detail'), ]
This URLconf defines three URL patterns, all targeting a view:
url(r'^$', home, name='home'),
The regex contains a start anchor '^', immediately followed by an end anchor '$'. This pattern will match requests where the URL path is an empty string, and route them to the
home view defined in
url(r'^about/$', about, name='about'),
This regex contains a start anchor, followed by the literal string
about/, and the end anchor. This will match the URL
/about/ and route it to the
about view. Since every non-empty URL start with a
/, Django conveniently cuts of the first slash for you.
url(r'^blog/(?P<id>\d+)/$', blog_detail, name='blog-detail'),
This regex is a bit more complex. It defines the start anchor and the literal string
blog/, like the previous pattern. The next part,
(?P<id>\d+), is called a capturing group. A capturing group, like its name suggest, captures a part of the string, and Django passes the captured string as an argument to the view function.
The syntax of a capturing group is
name defines the name of the group, which is also the name that Django uses to pass the argument to the view. The pattern defines which characters are matched by the group.
In this case, the name is
id, so the function
blog_detail must accept a parameter named
id. The pattern is
\d signifies that the pattern only matches number characters.
+ signifies that the pattern must match one or more characters.
Some common patterns:
|id||One or more numerical characters|
|slug||One or more alphanumerical characters, underscores or dashes|
|year (long)||Four numbers, zero through nine|
day of month
|Two numbers, zero through nine|
|path segment||Anything except a slash|
The capturing group in the
blog-detail pattern is followed by a literal
/, and the end anchor.
Valid URLs include:
/blog/1/ # passes id='1'
/blog/42/ # passes id='42'
Invalid URLs are for example:
/blog/a/ # 'a' does not match '\d'
/blog// # no characters in the capturing group does not match '+'
Django processes each URL pattern in the same order they are defined in
urlpatterns. This is important if multiple patterns can match the same URL. For example:
urlpatterns = [ url(r'blog/(?P<slug>[\w-]+)/$', blog_detail, name='blog-detail'), url(r'blog/overview/$', blog_overview, name='blog-overview'), ]
In the above URLconf, the second pattern is not reachable. The pattern would match the URL
/blog/overview/, but instead of calling the
blog_overview view, the URL will first match the
blog-detail pattern and call the
blog_detail view with an argument
To make sure that the URL
/blog/overview/ is routed to the
blog_overview view, the pattern should be put above the
urlpatterns = [ url(r'blog/overview/$', blog_overview, name='blog-overview'), url(r'blog/(?P<slug>[\w-]+)/$', blog_detail, name='blog-detail'), ]