django.urls utility functions¶reverse()¶If you need to use something similar to the url template tag in
your code, Django provides the following function:
viewname can be a URL pattern name or the
callable view object. For example, given the following url:
from news import views
path("archive/", views.archive, name="news-archive")
you can use any of the following to reverse the URL:
# using the named URL
reverse("news-archive")
# passing a callable object
# (This is discouraged because you can't reverse namespaced views this way.)
from news import views
reverse(views.archive)
If the URL accepts arguments, you may pass them in args. For example:
from django.urls import reverse
def myview(request):
return HttpResponseRedirect(reverse("arch-summary", args=[1945]))
You can also pass kwargs instead of args. For example:
>>> reverse("admin:app_list", kwargs={"app_label": "auth"})
'/admin/auth/'
args and kwargs cannot be passed to reverse() at the same time.
If no match can be made, reverse() raises a
NoReverseMatch exception.
The reverse() function can reverse a large variety of regular expression
patterns for URLs, but not every possible one. The main restriction at the
moment is that the pattern cannot contain alternative choices using the
vertical bar ("|") character. You can quite happily use such patterns for
matching against incoming URLs and sending them off to views, but you cannot
reverse such patterns.
The current_app argument allows you to provide a hint to the resolver
indicating the application to which the currently executing view belongs.
This current_app argument is used as a hint to resolve application
namespaces into URLs on specific application instances, according to the
namespaced URL resolution strategy.
The urlconf argument is the URLconf module containing the URL patterns to
use for reversing. By default, the root URLconf for the current thread is used.
Note
The string returned by reverse() is already
urlquoted. For example:
>>> reverse("cities", args=["Orléans"])
'.../Orl%C3%A9ans/'
Applying further encoding (such as urllib.parse.quote()) to the output
of reverse() may produce undesirable results.
reverse_lazy()¶A lazily evaluated version of reverse().
It is useful for when you need to use a URL reversal before your project's URLConf is loaded. Some common cases where this function is necessary are:
providing a reversed URL as the url attribute of a generic class-based
view.
providing a reversed URL to a decorator (such as the login_url argument
for the django.contrib.auth.decorators.permission_required()
decorator).
providing a reversed URL as a default value for a parameter in a function's signature.
resolve()¶The resolve() function can be used for resolving URL paths to the
corresponding view functions. It has the following signature:
path is the URL path you want to resolve. As with
reverse(), you don't need to worry about the urlconf
parameter. The function returns a ResolverMatch object that allows you
to access various metadata about the resolved URL.
If the URL does not resolve, the function raises a
Resolver404 exception (a subclass of
Http404) .
The view function that would be used to serve the URL
The arguments that would be passed to the view function, as parsed from the URL.
All keyword arguments that would be passed to the view function, i.e.
captured_kwargs and
extra_kwargs.
The captured keyword arguments that would be passed to the view function, as parsed from the URL.
The additional keyword arguments that would be passed to the view function.
The name of the URL pattern that matches the URL.
The route of the matching URL pattern.
For example, if path('users/<id>/', ...) is the matching pattern,
route will contain 'users/<id>/'.
The list of URL patterns tried before the URL either matched one or exhausted available patterns.
The application namespace for the URL pattern that matches the URL.
The list of individual namespace components in the full
application namespace for the URL pattern that matches the URL.
For example, if the app_name is 'foo:bar', then app_names
will be ['foo', 'bar'].
The instance namespace for the URL pattern that matches the URL.
The list of individual namespace components in the full
instance namespace for the URL pattern that matches the URL.
i.e., if the namespace is foo:bar, then namespaces will be
['foo', 'bar'].
The name of the view that matches the URL, including the namespace if there is one.
A ResolverMatch object can then be interrogated to provide
information about the URL pattern that matches a URL:
# Resolve a URL
match = resolve("/some/path/")
# Print the URL pattern that matches the URL
print(match.url_name)
A ResolverMatch object can also be assigned to a triple:
func, args, kwargs = resolve("/some/path/")
One possible use of resolve() would be to test whether a
view would raise a Http404 error before redirecting to it:
from urllib.parse import urlparse
from django.urls import resolve
from django.http import Http404, HttpResponseRedirect
def myview(request):
next = request.META.get("HTTP_REFERER", None) or "/"
response = HttpResponseRedirect(next)
# modify the request and response as required, e.g. change locale
# and set corresponding locale cookie
view, args, kwargs = resolve(urlparse(next)[2])
kwargs["request"] = request
try:
view(*args, **kwargs)
except Http404:
return HttpResponseRedirect("/")
return response
get_script_prefix()¶Normally, you should always use reverse() to define URLs
within your application. However, if your application constructs part of the
URL hierarchy itself, you may occasionally need to generate URLs. In that
case, you need to be able to find the base URL of the Django project within
its web server (normally, reverse() takes care of this for
you). In that case, you can call get_script_prefix(), which will return
the script prefix portion of the URL for your Django project. If your Django
project is at the root of its web server, this is always "/".
Warning
This function cannot be used outside of the request-response cycle since it relies on values initialized during that cycle.
Jan 15, 2024