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``django.urls`` utility functions

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.. module:: django.urls

``reverse()``

=============

If you need to use something similar to the :ttag:`url` template tag in

your code, Django provides the following function:

.. function:: reverse(viewname, urlconf=None, args=None, kwargs=None, current_app=None)

``viewname`` can be a :ref:`URL pattern name <naming-url-patterns>` 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

:class:`~django.urls.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

:ref:`namespaced URL resolution strategy <topics-http-reversing-url-namespaces>`.

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

    :ref:`urlquoted <uri-and-iri-handling>`. For example::

        >>> reverse('cities', args=['Orléans'])

        '.../Orl%C3%A9ans/'

    Applying further encoding (such as :func:`urllib.parse.quote`) to the output

    of ``reverse()`` may produce undesirable results.

``reverse_lazy()``

==================

A lazily evaluated version of `reverse()`_.

.. function:: reverse_lazy(viewname, urlconf=None, args=None, kwargs=None, current_app=None)

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 :func:`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:

.. function:: resolve(path, urlconf=None)

``path`` is the URL path you want to resolve. As with

:func:`~django.urls.reverse`, you don't need to worry about the ``urlconf``

parameter. The function returns a :class:`ResolverMatch` object that allows you

to access various metadata about the resolved URL.

If the URL does not resolve, the function raises a

:exc:`~django.urls.Resolver404` exception (a subclass of

:class:`~django.http.Http404`) .

.. class:: ResolverMatch

    .. attribute:: ResolverMatch.func

        The view function that would be used to serve the URL

    .. attribute:: ResolverMatch.args

        The arguments that would be passed to the view function, as

        parsed from the URL.

    .. attribute:: ResolverMatch.kwargs

        All keyword arguments that would be passed to the view function, i.e.

        :attr:`~ResolverMatch.captured_kwargs` and

        :attr:`~ResolverMatch.extra_kwargs`.

    .. attribute:: ResolverMatch.captured_kwargs

        .. versionadded:: 4.1

        The captured keyword arguments that would be passed to the view

        function, as parsed from the URL.

    .. attribute:: ResolverMatch.extra_kwargs

        .. versionadded:: 4.1

        The additional keyword arguments that would be passed to the view

        function.

    .. attribute:: ResolverMatch.url_name

        The name of the URL pattern that matches the URL.

    .. attribute:: ResolverMatch.route

        The route of the matching URL pattern.

        For example, if ``path('users/<id>/', ...)`` is the matching pattern,

        ``route`` will contain ``'users/<id>/'``.

    .. attribute:: ResolverMatch.tried

        The list of URL patterns tried before the URL either matched one or

        exhausted available patterns.

    .. attribute:: ResolverMatch.app_name

        The application namespace for the URL pattern that matches the

        URL.

    .. attribute:: ResolverMatch.app_names

        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']``.

    .. attribute:: ResolverMatch.namespace

        The instance namespace for the URL pattern that matches the

        URL.

    .. attribute:: ResolverMatch.namespaces

        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']``.

    .. attribute:: ResolverMatch.view_name

        The name of the view that matches the URL, including the namespace if

        there is one.

A :class:`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 :class:`ResolverMatch` object can also be assigned to a triple::

    func, args, kwargs = resolve('/some/path/')

One possible use of :func:`~django.urls.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()``

=======================

.. function:: get_script_prefix()

Normally, you should always use :func:`~django.urls.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, :func:`~django.urls.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 ``"/"``.