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Trying to move most of the introductory example stuff up to the top and pushing the reference bits further down.
1024 lines
37 KiB
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1024 lines
37 KiB
Plaintext
==============
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URL dispatcher
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==============
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.. module:: django.core.urlresolvers
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A clean, elegant URL scheme is an important detail in a high-quality Web
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application. Django lets you design URLs however you want, with no framework
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limitations.
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There's no ``.php`` or ``.cgi`` required, and certainly none of that
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``0,2097,1-1-1928,00`` nonsense.
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See `Cool URIs don't change`_, by World Wide Web creator Tim Berners-Lee, for
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excellent arguments on why URLs should be clean and usable.
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.. _Cool URIs don't change: http://www.w3.org/Provider/Style/URI
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Overview
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========
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To design URLs for an app, you create a Python module informally called a
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**URLconf** (URL configuration). This module is pure Python code and is a
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simple mapping between URL patterns (simple regular expressions) to Python
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functions (your views).
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This mapping can be as short or as long as needed. It can reference other
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mappings. And, because it's pure Python code, it can be constructed
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dynamically.
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.. versionadded:: 1.4
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Django also provides a way to translate URLs according to the active
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language. See the :ref:`internationalization documentation
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<url-internationalization>` for more information.
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.. _how-django-processes-a-request:
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How Django processes a request
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==============================
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When a user requests a page from your Django-powered site, this is the
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algorithm the system follows to determine which Python code to execute:
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1. Django determines the root URLconf module to use. Ordinarily,
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this is the value of the :setting:`ROOT_URLCONF` setting, but if the incoming
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``HttpRequest`` object has an attribute called ``urlconf`` (set by
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middleware :ref:`request processing <request-middleware>`), its value
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will be used in place of the :setting:`ROOT_URLCONF` setting.
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2. Django loads that Python module and looks for the variable
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``urlpatterns``. This should be a Python list, in the format returned by
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the function :func:`django.conf.urls.patterns`.
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3. Django runs through each URL pattern, in order, and stops at the first
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one that matches the requested URL.
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4. Once one of the regexes matches, Django imports and calls the given
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view, which is a simple Python function. The view gets passed an
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:class:`~django.http.HttpRequest` as its first argument and any values
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captured in the regex as remaining arguments.
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5. If no regex matches, or if an exception is raised during any
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point in this process, Django invokes an appropriate
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error-handling view. See `Error handling`_ below.
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Example
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=======
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Here's a sample URLconf::
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from django.conf.urls import patterns, url, include
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urlpatterns = patterns('',
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(r'^articles/2003/$', 'news.views.special_case_2003'),
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(r'^articles/(\d{4})/$', 'news.views.year_archive'),
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(r'^articles/(\d{4})/(\d{2})/$', 'news.views.month_archive'),
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(r'^articles/(\d{4})/(\d{2})/(\d+)/$', 'news.views.article_detail'),
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)
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Notes:
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* To capture a value from the URL, just put parenthesis around it.
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* There's no need to add a leading slash, because every URL has that. For
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example, it's ``^articles``, not ``^/articles``.
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* The ``'r'`` in front of each regular expression string is optional but
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recommended. It tells Python that a string is "raw" -- that nothing in
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the string should be escaped. See `Dive Into Python's explanation`_.
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Example requests:
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* A request to ``/articles/2005/03/`` would match the third entry in the
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list. Django would call the function
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``news.views.month_archive(request, '2005', '03')``.
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* ``/articles/2005/3/`` would not match any URL patterns, because the
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third entry in the list requires two digits for the month.
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* ``/articles/2003/`` would match the first pattern in the list, not the
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second one, because the patterns are tested in order, and the first one
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is the first test to pass. Feel free to exploit the ordering to insert
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special cases like this.
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* ``/articles/2003`` would not match any of these patterns, because each
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pattern requires that the URL end with a slash.
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* ``/articles/2003/03/03/`` would match the final pattern. Django would call
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the function ``news.views.article_detail(request, '2003', '03', '03')``.
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.. _Dive Into Python's explanation: http://diveintopython.net/regular_expressions/street_addresses.html#re.matching.2.3
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Named groups
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============
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The above example used simple, *non-named* regular-expression groups (via
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parenthesis) to capture bits of the URL and pass them as *positional* arguments
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to a view. In more advanced usage, it's possible to use *named*
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regular-expression groups to capture URL bits and pass them as *keyword*
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arguments to a view.
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In Python regular expressions, the syntax for named regular-expression groups
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is ``(?P<name>pattern)``, where ``name`` is the name of the group and
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``pattern`` is some pattern to match.
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Here's the above example URLconf, rewritten to use named groups::
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urlpatterns = patterns('',
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(r'^articles/2003/$', 'news.views.special_case_2003'),
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(r'^articles/(?P<year>\d{4})/$', 'news.views.year_archive'),
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(r'^articles/(?P<year>\d{4})/(?P<month>\d{2})/$', 'news.views.month_archive'),
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(r'^articles/(?P<year>\d{4})/(?P<month>\d{2})/(?P<day>\d{2})/$', 'news.views.article_detail'),
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)
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This accomplishes exactly the same thing as the previous example, with one
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subtle difference: The captured values are passed to view functions as keyword
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arguments rather than positional arguments. For example:
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* A request to ``/articles/2005/03/`` would call the function
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``news.views.month_archive(request, year='2005', month='03')``, instead
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of ``news.views.month_archive(request, '2005', '03')``.
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* A request to ``/articles/2003/03/03/`` would call the function
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``news.views.article_detail(request, year='2003', month='03', day='03')``.
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In practice, this means your URLconfs are slightly more explicit and less prone
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to argument-order bugs -- and you can reorder the arguments in your views'
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function definitions. Of course, these benefits come at the cost of brevity;
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some developers find the named-group syntax ugly and too verbose.
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The matching/grouping algorithm
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-------------------------------
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Here's the algorithm the URLconf parser follows, with respect to named groups
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vs. non-named groups in a regular expression:
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1. If there are any named arguments, it will use those, ignoring non-named
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arguments.
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2. Otherwise, it will pass all non-named arguments as positional arguments.
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In both cases, any extra keyword arguments that have been given as per `Passing extra options to view functions`_ (below) will also be passed to the view.
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What the URLconf searches against
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=================================
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The URLconf searches against the requested URL, as a normal Python string. This
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does not include GET or POST parameters, or the domain name.
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For example, in a request to ``http://www.example.com/myapp/``, the URLconf
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will look for ``myapp/``.
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In a request to ``http://www.example.com/myapp/?page=3``, the URLconf will look
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for ``myapp/``.
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The URLconf doesn't look at the request method. In other words, all request
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methods -- ``POST``, ``GET``, ``HEAD``, etc. -- will be routed to the same
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function for the same URL.
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Notes on capturing text in URLs
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===============================
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Each captured argument is sent to the view as a plain Python string, regardless
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of what sort of match the regular expression makes. For example, in this
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URLconf line::
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(r'^articles/(?P<year>\d{4})/$', 'news.views.year_archive'),
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...the ``year`` argument to ``news.views.year_archive()`` will be a string, not
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an integer, even though the ``\d{4}`` will only match integer strings.
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A convenient trick is to specify default parameters for your views' arguments.
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Here's an example URLconf and view::
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# URLconf
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urlpatterns = patterns('',
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(r'^blog/$', 'blog.views.page'),
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(r'^blog/page(?P<num>\d+)/$', 'blog.views.page'),
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)
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# View (in blog/views.py)
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def page(request, num="1"):
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# Output the appropriate page of blog entries, according to num.
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In the above example, both URL patterns point to the same view --
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``blog.views.page`` -- but the first pattern doesn't capture anything from the
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URL. If the first pattern matches, the ``page()`` function will use its
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default argument for ``num``, ``"1"``. If the second pattern matches,
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``page()`` will use whatever ``num`` value was captured by the regex.
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Performance
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===========
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Each regular expression in a ``urlpatterns`` is compiled the first time it's
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accessed. This makes the system blazingly fast.
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Syntax of the urlpatterns variable
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==================================
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``urlpatterns`` should be a Python list, in the format returned by the function
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:func:`django.conf.urls.patterns`. Always use ``patterns()`` to create
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the ``urlpatterns`` variable.
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``django.conf.urls`` utility functions
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======================================
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.. module:: django.conf.urls
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.. deprecated:: 1.4
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Starting with Django 1.4 functions ``patterns``, ``url``, ``include`` plus
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the ``handler*`` symbols described below live in the ``django.conf.urls``
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module.
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Until Django 1.3 they were located in ``django.conf.urls.defaults``. You
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still can import them from there but it will be removed in Django 1.6.
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patterns
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--------
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.. function:: patterns(prefix, pattern_description, ...)
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A function that takes a prefix, and an arbitrary number of URL patterns, and
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returns a list of URL patterns in the format Django needs.
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The first argument to ``patterns()`` is a string ``prefix``. See
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`The view prefix`_ below.
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The remaining arguments should be tuples in this format::
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(regular expression, Python callback function [, optional_dictionary [, optional_name]])
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The ``optional_dictionary`` and ``optional_name`` parameters are described in
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`Passing extra options to view functions`_ below.
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.. note::
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Because `patterns()` is a function call, it accepts a maximum of 255
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arguments (URL patterns, in this case). This is a limit for all Python
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function calls. This is rarely a problem in practice, because you'll
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typically structure your URL patterns modularly by using `include()`
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sections. However, on the off-chance you do hit the 255-argument limit,
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realize that `patterns()` returns a Python list, so you can split up the
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construction of the list.
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::
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urlpatterns = patterns('',
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...
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)
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urlpatterns += patterns('',
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...
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)
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Python lists have unlimited size, so there's no limit to how many URL
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patterns you can construct. The only limit is that you can only create 254
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at a time (the 255th argument is the initial prefix argument).
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url
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---
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.. function:: url(regex, view, kwargs=None, name=None, prefix='')
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You can use the ``url()`` function, instead of a tuple, as an argument to
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``patterns()``. This is convenient if you want to specify a name without the
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optional extra arguments dictionary. For example::
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urlpatterns = patterns('',
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url(r'^index/$', index_view, name="main-view"),
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...
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)
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This function takes five arguments, most of which are optional::
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url(regex, view, kwargs=None, name=None, prefix='')
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See `Naming URL patterns`_ for why the ``name`` parameter is useful.
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The ``prefix`` parameter has the same meaning as the first argument to
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``patterns()`` and is only relevant when you're passing a string as the
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``view`` parameter.
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include
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-------
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.. function:: include(<module or pattern_list>)
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A function that takes a full Python import path to another URLconf module that
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should be "included" in this place.
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:func:`include` also accepts as an argument an iterable that returns URL
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patterns.
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See `Including other URLconfs`_ below.
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Error handling
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==============
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When Django can't find a regex matching the requested URL, or when an
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exception is raised, Django will invoke an error-handling view. The
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views to use for these cases are specified by three variables which can
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be set in your root URLconf. Setting these variables in any other
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URLconf will have no effect.
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See the documentation on :ref:`customizing error views
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<customizing-error-views>` for more details.
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handler403
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----------
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.. data:: handler403
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A callable, or a string representing the full Python import path to the view
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that should be called if the user doesn't have the permissions required to
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access a resource.
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By default, this is ``'django.views.defaults.permission_denied'``. That default
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value should suffice.
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See the documentation about :ref:`the 403 (HTTP Forbidden) view
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<http_forbidden_view>` for more information.
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.. versionadded:: 1.4
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``handler403`` is new in Django 1.4.
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handler404
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----------
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.. data:: handler404
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A callable, or a string representing the full Python import path to the view
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that should be called if none of the URL patterns match.
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By default, this is ``'django.views.defaults.page_not_found'``. That default
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value should suffice.
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See the documentation about :ref:`the 404 (HTTP Not Found) view
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<http_not_found_view>` for more information.
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handler500
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----------
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.. data:: handler500
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A callable, or a string representing the full Python import path to the view
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that should be called in case of server errors. Server errors happen when you
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have runtime errors in view code.
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By default, this is ``'django.views.defaults.server_error'``. That default
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value should suffice.
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See the documentation about :ref:`the 500 (HTTP Internal Server Error) view
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<http_internal_server_error_view>` for more information.
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The view prefix
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===============
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You can specify a common prefix in your ``patterns()`` call, to cut down on
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code duplication.
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Here's the example URLconf from the :doc:`Django overview </intro/overview>`::
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from django.conf.urls import patterns, url, include
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urlpatterns = patterns('',
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(r'^articles/(\d{4})/$', 'news.views.year_archive'),
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(r'^articles/(\d{4})/(\d{2})/$', 'news.views.month_archive'),
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(r'^articles/(\d{4})/(\d{2})/(\d+)/$', 'news.views.article_detail'),
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)
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In this example, each view has a common prefix -- ``'news.views'``.
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Instead of typing that out for each entry in ``urlpatterns``, you can use the
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first argument to the ``patterns()`` function to specify a prefix to apply to
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each view function.
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With this in mind, the above example can be written more concisely as::
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from django.conf.urls import patterns, url, include
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urlpatterns = patterns('news.views',
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(r'^articles/(\d{4})/$', 'year_archive'),
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(r'^articles/(\d{4})/(\d{2})/$', 'month_archive'),
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(r'^articles/(\d{4})/(\d{2})/(\d+)/$', 'article_detail'),
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)
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Note that you don't put a trailing dot (``"."``) in the prefix. Django puts
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that in automatically.
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Multiple view prefixes
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----------------------
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In practice, you'll probably end up mixing and matching views to the point
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where the views in your ``urlpatterns`` won't have a common prefix. However,
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you can still take advantage of the view prefix shortcut to remove duplication.
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Just add multiple ``patterns()`` objects together, like this:
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Old::
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from django.conf.urls import patterns, url, include
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urlpatterns = patterns('',
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(r'^$', 'myapp.views.app_index'),
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(r'^(?P<year>\d{4})/(?P<month>[a-z]{3})/$', 'myapp.views.month_display'),
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(r'^tag/(?P<tag>\w+)/$', 'weblog.views.tag'),
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)
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New::
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from django.conf.urls import patterns, url, include
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urlpatterns = patterns('myapp.views',
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(r'^$', 'app_index'),
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(r'^(?P<year>\d{4})/(?P<month>[a-z]{3})/$','month_display'),
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)
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urlpatterns += patterns('weblog.views',
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(r'^tag/(?P<tag>\w+)/$', 'tag'),
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)
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Including other URLconfs
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========================
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At any point, your ``urlpatterns`` can "include" other URLconf modules. This
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essentially "roots" a set of URLs below other ones.
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For example, here's an excerpt of the URLconf for the `Django Web site`_
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itself. It includes a number of other URLconfs::
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from django.conf.urls import patterns, url, include
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urlpatterns = patterns('',
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# ... snip ...
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(r'^comments/', include('django.contrib.comments.urls')),
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(r'^community/', include('django_website.aggregator.urls')),
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(r'^contact/', include('django_website.contact.urls')),
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(r'^r/', include('django.conf.urls.shortcut')),
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# ... snip ...
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)
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Note that the regular expressions in this example don't have a ``$``
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(end-of-string match character) but do include a trailing slash. Whenever
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Django encounters ``include()``, it chops off whatever part of the URL matched
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up to that point and sends the remaining string to the included URLconf for
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further processing.
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Another possibility is to include additional URL patterns not by specifying the
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URLconf Python module defining them as the `include`_ argument but by using
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directly the pattern list as returned by `patterns`_ instead. For example::
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from django.conf.urls import patterns, url, include
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extra_patterns = patterns('',
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url(r'^reports/(?P<id>\d+)/$', 'credit.views.report', name='credit-reports'),
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url(r'^charge/$', 'credit.views.charge', name='credit-charge'),
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)
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urlpatterns = patterns('',
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url(r'^$', 'apps.main.views.homepage', name='site-homepage'),
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(r'^help/', include('apps.help.urls')),
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(r'^credit/', include(extra_patterns)),
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)
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This approach can be seen in use when you deploy an instance of the Django
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Admin application. The Django Admin is deployed as instances of a
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:class:`~django.contrib.admin.AdminSite`; each
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:class:`~django.contrib.admin.AdminSite` instance has an attribute ``urls``
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that returns the url patterns available to that instance. It is this attribute
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that you ``include()`` into your projects ``urlpatterns`` when you deploy the
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admin instance.
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.. _`Django Web site`: https://www.djangoproject.com/
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Captured parameters
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-------------------
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An included URLconf receives any captured parameters from parent URLconfs, so
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the following example is valid::
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# In settings/urls/main.py
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urlpatterns = patterns('',
|
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(r'^(?P<username>\w+)/blog/', include('foo.urls.blog')),
|
|
)
|
|
|
|
# In foo/urls/blog.py
|
|
urlpatterns = patterns('foo.views',
|
|
(r'^$', 'blog.index'),
|
|
(r'^archive/$', 'blog.archive'),
|
|
)
|
|
|
|
In the above example, the captured ``"username"`` variable is passed to the
|
|
included URLconf, as expected.
|
|
|
|
.. _topics-http-defining-url-namespaces:
|
|
|
|
Defining URL namespaces
|
|
-----------------------
|
|
|
|
When you need to deploy multiple instances of a single application, it can be
|
|
helpful to be able to differentiate between instances. This is especially
|
|
important when using :ref:`named URL patterns <naming-url-patterns>`, since
|
|
multiple instances of a single application will share named URLs. Namespaces
|
|
provide a way to tell these named URLs apart.
|
|
|
|
A URL namespace comes in two parts, both of which are strings:
|
|
|
|
* An **application namespace**. This describes the name of the application
|
|
that is being deployed. Every instance of a single application will have
|
|
the same application namespace. For example, Django's admin application
|
|
has the somewhat predictable application namespace of ``admin``.
|
|
|
|
* An **instance namespace**. This identifies a specific instance of an
|
|
application. Instance namespaces should be unique across your entire
|
|
project. However, an instance namespace can be the same as the
|
|
application namespace. This is used to specify a default instance of an
|
|
application. For example, the default Django Admin instance has an
|
|
instance namespace of ``admin``.
|
|
|
|
URL Namespaces can be specified in two ways.
|
|
|
|
Firstly, you can provide the application and instance namespace as arguments
|
|
to ``include()`` when you construct your URL patterns. For example,::
|
|
|
|
(r'^help/', include('apps.help.urls', namespace='foo', app_name='bar')),
|
|
|
|
This will include the URLs defined in ``apps.help.urls`` into the application
|
|
namespace ``bar``, with the instance namespace ``foo``.
|
|
|
|
Secondly, you can include an object that contains embedded namespace data. If
|
|
you ``include()`` a ``patterns`` object, that object will be added to the
|
|
global namespace. However, you can also ``include()`` an object that contains
|
|
a 3-tuple containing::
|
|
|
|
(<patterns object>, <application namespace>, <instance namespace>)
|
|
|
|
This will include the nominated URL patterns into the given application and
|
|
instance namespace. For example, the ``urls`` attribute of Django's
|
|
:class:`~django.contrib.admin.AdminSite` object returns a 3-tuple that contains
|
|
all the patterns in an admin site, plus the name of the admin instance, and the
|
|
application namespace ``admin``.
|
|
|
|
Once you have defined namespaced URLs, you can reverse them. For details on
|
|
reversing namespaced urls, see the documentation on :ref:`reversing namespaced
|
|
URLs <topics-http-reversing-url-namespaces>`.
|
|
|
|
Passing extra options to view functions
|
|
=======================================
|
|
|
|
URLconfs have a hook that lets you pass extra arguments to your view functions,
|
|
as a Python dictionary.
|
|
|
|
Any URLconf tuple can have an optional third element, which should be a
|
|
dictionary of extra keyword arguments to pass to the view function.
|
|
|
|
For example::
|
|
|
|
urlpatterns = patterns('blog.views',
|
|
(r'^blog/(?P<year>\d{4})/$', 'year_archive', {'foo': 'bar'}),
|
|
)
|
|
|
|
In this example, for a request to ``/blog/2005/``, Django will call
|
|
``blog.views.year_archive(year='2005', foo='bar')``.
|
|
|
|
This technique is used in the
|
|
:doc:`syndication framework </ref/contrib/syndication>` to pass metadata and
|
|
options to views.
|
|
|
|
.. admonition:: Dealing with conflicts
|
|
|
|
It's possible to have a URL pattern which captures named keyword arguments,
|
|
and also passes arguments with the same names in its dictionary of extra
|
|
arguments. When this happens, the arguments in the dictionary will be used
|
|
instead of the arguments captured in the URL.
|
|
|
|
Passing extra options to ``include()``
|
|
--------------------------------------
|
|
|
|
Similarly, you can pass extra options to ``include()``. When you pass extra
|
|
options to ``include()``, *each* line in the included URLconf will be passed
|
|
the extra options.
|
|
|
|
For example, these two URLconf sets are functionally identical:
|
|
|
|
Set one::
|
|
|
|
# main.py
|
|
urlpatterns = patterns('',
|
|
(r'^blog/', include('inner'), {'blogid': 3}),
|
|
)
|
|
|
|
# inner.py
|
|
urlpatterns = patterns('',
|
|
(r'^archive/$', 'mysite.views.archive'),
|
|
(r'^about/$', 'mysite.views.about'),
|
|
)
|
|
|
|
Set two::
|
|
|
|
# main.py
|
|
urlpatterns = patterns('',
|
|
(r'^blog/', include('inner')),
|
|
)
|
|
|
|
# inner.py
|
|
urlpatterns = patterns('',
|
|
(r'^archive/$', 'mysite.views.archive', {'blogid': 3}),
|
|
(r'^about/$', 'mysite.views.about', {'blogid': 3}),
|
|
)
|
|
|
|
Note that extra options will *always* be passed to *every* line in the included
|
|
URLconf, regardless of whether the line's view actually accepts those options
|
|
as valid. For this reason, this technique is only useful if you're certain that
|
|
every view in the included URLconf accepts the extra options you're passing.
|
|
|
|
Passing callable objects instead of strings
|
|
===========================================
|
|
|
|
Some developers find it more natural to pass the actual Python function object
|
|
rather than a string containing the path to its module. This alternative is
|
|
supported -- you can pass any callable object as the view.
|
|
|
|
For example, given this URLconf in "string" notation::
|
|
|
|
urlpatterns = patterns('',
|
|
(r'^archive/$', 'mysite.views.archive'),
|
|
(r'^about/$', 'mysite.views.about'),
|
|
(r'^contact/$', 'mysite.views.contact'),
|
|
)
|
|
|
|
You can accomplish the same thing by passing objects rather than strings. Just
|
|
be sure to import the objects::
|
|
|
|
from mysite.views import archive, about, contact
|
|
|
|
urlpatterns = patterns('',
|
|
(r'^archive/$', archive),
|
|
(r'^about/$', about),
|
|
(r'^contact/$', contact),
|
|
)
|
|
|
|
The following example is functionally identical. It's just a bit more compact
|
|
because it imports the module that contains the views, rather than importing
|
|
each view individually::
|
|
|
|
from mysite import views
|
|
|
|
urlpatterns = patterns('',
|
|
(r'^archive/$', views.archive),
|
|
(r'^about/$', views.about),
|
|
(r'^contact/$', views.contact),
|
|
)
|
|
|
|
The style you use is up to you.
|
|
|
|
Note that if you use this technique -- passing objects rather than strings --
|
|
the view prefix (as explained in "The view prefix" above) will have no effect.
|
|
|
|
.. _naming-url-patterns:
|
|
|
|
Naming URL patterns
|
|
===================
|
|
|
|
It's fairly common to use the same view function in multiple URL patterns in
|
|
your URLconf. For example, these two URL patterns both point to the ``archive``
|
|
view::
|
|
|
|
urlpatterns = patterns('',
|
|
(r'^archive/(\d{4})/$', archive),
|
|
(r'^archive-summary/(\d{4})/$', archive, {'summary': True}),
|
|
)
|
|
|
|
This is completely valid, but it leads to problems when you try to do reverse
|
|
URL matching (through the ``permalink()`` decorator or the :ttag:`url` template
|
|
tag). Continuing this example, if you wanted to retrieve the URL for the
|
|
``archive`` view, Django's reverse URL matcher would get confused, because *two*
|
|
URL patterns point at that view.
|
|
|
|
To solve this problem, Django supports **named URL patterns**. That is, you can
|
|
give a name to a URL pattern in order to distinguish it from other patterns
|
|
using the same view and parameters. Then, you can use this name in reverse URL
|
|
matching.
|
|
|
|
Here's the above example, rewritten to use named URL patterns::
|
|
|
|
urlpatterns = patterns('',
|
|
url(r'^archive/(\d{4})/$', archive, name="full-archive"),
|
|
url(r'^archive-summary/(\d{4})/$', archive, {'summary': True}, "arch-summary"),
|
|
)
|
|
|
|
With these names in place (``full-archive`` and ``arch-summary``), you can
|
|
target each pattern individually by using its name:
|
|
|
|
.. code-block:: html+django
|
|
|
|
{% url 'arch-summary' 1945 %}
|
|
{% url 'full-archive' 2007 %}
|
|
|
|
Even though both URL patterns refer to the ``archive`` view here, using the
|
|
``name`` parameter to ``url()`` allows you to tell them apart in templates.
|
|
|
|
The string used for the URL name can contain any characters you like. You are
|
|
not restricted to valid Python names.
|
|
|
|
.. note::
|
|
|
|
When you name your URL patterns, make sure you use names that are unlikely
|
|
to clash with any other application's choice of names. If you call your URL
|
|
pattern ``comment``, and another application does the same thing, there's
|
|
no guarantee which URL will be inserted into your template when you use
|
|
this name.
|
|
|
|
Putting a prefix on your URL names, perhaps derived from the application
|
|
name, will decrease the chances of collision. We recommend something like
|
|
``myapp-comment`` instead of ``comment``.
|
|
|
|
.. _topics-http-reversing-url-namespaces:
|
|
|
|
URL namespaces
|
|
--------------
|
|
|
|
Namespaced URLs are specified using the ``:`` operator. For example, the main
|
|
index page of the admin application is referenced using ``admin:index``. This
|
|
indicates a namespace of ``admin``, and a named URL of ``index``.
|
|
|
|
Namespaces can also be nested. The named URL ``foo:bar:whiz`` would look for
|
|
a pattern named ``whiz`` in the namespace ``bar`` that is itself defined within
|
|
the top-level namespace ``foo``.
|
|
|
|
When given a namespaced URL (e.g. ``myapp:index``) to resolve, Django splits
|
|
the fully qualified name into parts, and then tries the following lookup:
|
|
|
|
1. First, Django looks for a matching application namespace (in this
|
|
example, ``myapp``). This will yield a list of instances of that
|
|
application.
|
|
|
|
2. If there is a *current* application defined, Django finds and returns
|
|
the URL resolver for that instance. The *current* application can be
|
|
specified as an attribute on the template context - applications that
|
|
expect to have multiple deployments should set the ``current_app``
|
|
attribute on any ``Context`` or ``RequestContext`` that is used to
|
|
render a template.
|
|
|
|
The current application can also be specified manually as an argument
|
|
to the :func:`reverse()` function.
|
|
|
|
3. If there is no current application. Django looks for a default
|
|
application instance. The default application instance is the instance
|
|
that has an instance namespace matching the application namespace (in
|
|
this example, an instance of the ``myapp`` called ``myapp``).
|
|
|
|
4. If there is no default application instance, Django will pick the last
|
|
deployed instance of the application, whatever its instance name may be.
|
|
|
|
5. If the provided namespace doesn't match an application namespace in
|
|
step 1, Django will attempt a direct lookup of the namespace as an
|
|
instance namespace.
|
|
|
|
If there are nested namespaces, these steps are repeated for each part of the
|
|
namespace until only the view name is unresolved. The view name will then be
|
|
resolved into a URL in the namespace that has been found.
|
|
|
|
To show this resolution strategy in action, consider an example of two instances
|
|
of ``myapp``: one called ``foo``, and one called ``bar``. ``myapp`` has a main
|
|
index page with a URL named `index`. Using this setup, the following lookups are
|
|
possible:
|
|
|
|
* If one of the instances is current - say, if we were rendering a utility page
|
|
in the instance ``bar`` - ``myapp:index`` will resolve to the index page of
|
|
the instance ``bar``.
|
|
|
|
* If there is no current instance - say, if we were rendering a page
|
|
somewhere else on the site - ``myapp:index`` will resolve to the last
|
|
registered instance of ``myapp``. Since there is no default instance,
|
|
the last instance of ``myapp`` that is registered will be used. This could
|
|
be ``foo`` or ``bar``, depending on the order they are introduced into the
|
|
urlpatterns of the project.
|
|
|
|
* ``foo:index`` will always resolve to the index page of the instance ``foo``.
|
|
|
|
If there was also a default instance - i.e., an instance named `myapp` - the
|
|
following would happen:
|
|
|
|
* If one of the instances is current - say, if we were rendering a utility page
|
|
in the instance ``bar`` - ``myapp:index`` will resolve to the index page of
|
|
the instance ``bar``.
|
|
|
|
* If there is no current instance - say, if we were rendering a page somewhere
|
|
else on the site - ``myapp:index`` will resolve to the index page of the
|
|
default instance.
|
|
|
|
* ``foo:index`` will again resolve to the index page of the instance ``foo``.
|
|
|
|
|
|
``django.core.urlresolvers`` utility functions
|
|
==============================================
|
|
|
|
.. currentmodule:: 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
|
|
`URL pattern name`_. 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]))
|
|
|
|
.. _URL pattern name: `Naming URL patterns`_
|
|
|
|
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/')
|
|
|
|
.. versionchanged:: 1.3
|
|
Triple-assignment exists for backwards-compatibility. Prior to
|
|
Django 1.3, :func:`~django.core.urlresolvers.resolve` returned a
|
|
triple containing (view function, arguments, keyword arguments);
|
|
the :class:`ResolverMatch` object (as well as the namespace and pattern
|
|
information it provides) is not available in earlier Django releases.
|
|
|
|
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.
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However, if your application constructs part of the URL hierarchy itself, you
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may occasionally need to generate URLs. In that case, you need to be able to
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find the base URL of the Django project within its Web server
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(normally, :func:`~django.core.urlresolvers.reverse` takes care of this for
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you). In that case, you can call ``get_script_prefix()``, which will return the
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script prefix portion of the URL for your Django project. If your Django
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project is at the root of its Web server, this is always ``"/"``.
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