Refactored URL mapping documentation.

   signals

   templates/index

   unicode

   urlresolvers

   urls

   utils

   validators

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

``django.core.urlresolvers`` utility functions

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

.. module:: django.core.urlresolvers

reverse()

---------

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

your code, Django provides the following function (in the

:mod:`django.core.urlresolvers` module):

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

``viewname`` is either the function name (either a function reference, or the

string version of the name, if you used that form in ``urlpatterns``) or the

:ref:`URL pattern name <naming-url-patterns>`.  Normally, you won't need to

worry about the ``urlconf`` parameter and will only pass in the positional and

keyword arguments to use in the URL matching. For example::

    from django.core.urlresolvers import reverse

    def myview(request):

        return HttpResponseRedirect(reverse('arch-summary', args=[1945]))

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>`.

You can use ``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.

.. admonition:: Make sure your views are all correct.

    As part of working out which URL names map to which patterns, the

    ``reverse()`` function has to import all of your URLconf files and examine

    the name of each view. This involves importing each view function. If

    there are *any* errors whilst importing any of your view functions, it

    will cause ``reverse()`` to raise an error, even if that view function is

    not the one you are trying to reverse.

    Make sure that any views you reference in your URLconf files exist and can

    be imported correctly. Do not include lines that reference views you

    haven't written yet, because those views will not be importable.

.. note::

    The string returned by :meth:`~django.core.urlresolvers.reverse` is already

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

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

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

    Applying further encoding (such as :meth:`~django.utils.http.urlquote` or

    ``urllib.quote``) to the output of :meth:`~django.core.urlresolvers.reverse`

    may produce undesirable results.

reverse_lazy()

--------------

.. versionadded:: 1.4

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 :func:`django.core.urlresolvers.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.core.urlresolvers.reverse`, you don't need to

worry about the ``urlconf`` parameter. The function returns a

:class:`ResolverMatch` object that allows you

to access various meta-data about the resolved URL.

If the URL does not resolve, the function raises an

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

.. 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

        The keyword arguments that would be passed to the view

        function, as parsed from the URL.

    .. attribute:: ResolverMatch.url_name

        The name of the URL pattern that matches the URL.

    .. attribute:: ResolverMatch.app_name

        The application namespace for the URL pattern that matches the

        URL.

    .. 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']``.

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.core.urlresolvers.resolve` would be to test

whether a view would raise a ``Http404`` error before redirecting to it::

    from urlparse import urlparse

    from django.core.urlresolvers import resolve

    from django.http import HttpResponseRedirect, Http404

    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

permalink()

-----------

The :func:`django.db.models.permalink` decorator is useful for writing short

methods that return a full URL path. For example, a model's

``get_absolute_url()`` method. See :func:`django.db.models.permalink` for more.

get_script_prefix()

-------------------

.. function:: get_script_prefix()

Normally, you should always use :func:`~django.core.urlresolvers.reverse` or

:func:`~django.db.models.permalink` 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.core.urlresolvers.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 ``"/"``.

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

``django.conf.urls`` utility functions

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

.. module:: django.conf.urls

.. versionchanged:: 1.4

    Starting with Django 1.4 functions ``patterns``, ``url``, ``include`` plus

    the ``handler*`` symbols described below live in the ``django.conf.urls``

    module.

    Until Django 1.3 they were located in ``django.conf.urls.defaults``. You

    still can import them from there but it will be removed in Django 1.6.

patterns()

----------

.. function:: patterns(prefix, pattern_description, ...)

A function that takes a prefix, and an arbitrary number of URL patterns, and

returns a list of URL patterns in the format Django needs.

The first argument to ``patterns()`` is a string ``prefix``. See

:ref:`The view prefix <urlpatterns-view-prefix>`.

The remaining arguments should be tuples in this format::

    (regular expression, Python callback function [, optional_dictionary [, optional_name]])

The ``optional_dictionary`` and ``optional_name`` parameters are described in

:ref:`Passing extra options to view functions <views-extra-options>`.

.. note::

    Because `patterns()` is a function call, it accepts a maximum of 255

    arguments (URL patterns, in this case). This is a limit for all Python

    function calls. This is rarely a problem in practice, because you'll

    typically structure your URL patterns modularly by using `include()`

    sections. However, on the off-chance you do hit the 255-argument limit,

    realize that `patterns()` returns a Python list, so you can split up the

    construction of the list.

    ::

        urlpatterns = patterns('',

            ...

            )

        urlpatterns += patterns('',

            ...

            )

    Python lists have unlimited size, so there's no limit to how many URL

    patterns you can construct. The only limit is that you can only create 254

    at a time (the 255th argument is the initial prefix argument).

url()

-----

.. function:: url(regex, view, kwargs=None, name=None, prefix='')

You can use the ``url()`` function, instead of a tuple, as an argument to

``patterns()``. This is convenient if you want to specify a name without the

optional extra arguments dictionary. For example::

    urlpatterns = patterns('',

        url(r'^index/$', index_view, name="main-view"),

        ...

    )

This function takes five arguments, most of which are optional::

    url(regex, view, kwargs=None, name=None, prefix='')

See :ref:`Naming URL patterns <naming-url-patterns>` for why the ``name``

parameter is useful.

The ``prefix`` parameter has the same meaning as the first argument to

``patterns()`` and is only relevant when you're passing a string as the

``view`` parameter.

include()

---------

.. function:: include(<module or pattern_list>)

A function that takes a full Python import path to another URLconf module that

should be "included" in this place.

:func:`include` also accepts as an argument an iterable that returns URL

patterns.

See :ref:`Including other URLconfs <including-other-urlconfs>`.

handler403

----------

.. data:: handler403

A callable, or a string representing the full Python import path to the view

that should be called if the user doesn't have the permissions required to

access a resource.

By default, this is ``'django.views.defaults.permission_denied'``. That default

value should suffice.

See the documentation about :ref:`the 403 (HTTP Forbidden) view

<http_forbidden_view>` for more information.

.. versionadded:: 1.4

    ``handler403`` is new in Django 1.4.

handler404

----------

.. data:: handler404

A callable, or a string representing the full Python import path to the view

that should be called if none of the URL patterns match.

By default, this is ``'django.views.defaults.page_not_found'``. That default

value should suffice.

See the documentation about :ref:`the 404 (HTTP Not Found) view

<http_not_found_view>` for more information.

handler500

----------

.. data:: handler500

A callable, or a string representing the full Python import path to the view

that should be called in case of server errors. Server errors happen when you

have runtime errors in view code.

By default, this is ``'django.views.defaults.server_error'``. That default

value should suffice.

See the documentation about :ref:`the 500 (HTTP Internal Server Error) view

<http_internal_server_error_view>` for more information.