-
-
Notifications
You must be signed in to change notification settings - Fork 31.6k
/
urls.txt
966 lines (692 loc) · 36 KB
/
urls.txt
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
==============
URL dispatcher
==============
.. module:: django.core.urlresolvers
A clean, elegant URL scheme is an important detail in a high-quality Web
application. Django lets you design URLs however you want, with no framework
limitations.
There's no ``.php`` or ``.cgi`` required, and certainly none of that
``0,2097,1-1-1928,00`` nonsense.
See `Cool URIs don't change`_, by World Wide Web creator Tim Berners-Lee, for
excellent arguments on why URLs should be clean and usable.
.. _Cool URIs don't change: http://www.w3.org/Provider/Style/URI
Overview
========
To design URLs for an app, you create a Python module informally called a
**URLconf** (URL configuration). This module is pure Python code and
is a simple mapping between URL patterns (as simple regular expressions) to
Python callback functions (your views).
This mapping can be as short or as long as needed. It can reference other
mappings. And, because it's pure Python code, it can be constructed
dynamically.
.. _how-django-processes-a-request:
How Django processes a request
==============================
When a user requests a page from your Django-powered site, this is the
algorithm the system follows to determine which Python code to execute:
1. Django determines the root URLconf module to use. Ordinarily,
this is the value of the :setting:`ROOT_URLCONF` setting, but if the incoming
``HttpRequest`` object has an attribute called ``urlconf`` (set by
middleware :ref:`request processing <request-middleware>`), its value
will be used in place of the :setting:`ROOT_URLCONF` setting.
2. Django loads that Python module and looks for the variable
``urlpatterns``. This should be a Python list, in the format returned by
the function :func:`django.conf.urls.defaults.patterns`.
3. Django runs through each URL pattern, in order, and stops at the first
one that matches the requested URL.
4. Once one of the regexes matches, Django imports and calls the given
view, which is a simple Python function. The view gets passed an
:class:`~django.http.HttpRequest` as its first argument and any values
captured in the regex as remaining arguments.
5. If no regex matches, or if an exception is raised during any
point in this process, Django invokes an appropriate
error-handling view. See `Error handling`_ below.
Example
=======
Here's a sample URLconf::
from django.conf.urls.defaults import *
urlpatterns = patterns('',
(r'^articles/2003/$', 'news.views.special_case_2003'),
(r'^articles/(\d{4})/$', 'news.views.year_archive'),
(r'^articles/(\d{4})/(\d{2})/$', 'news.views.month_archive'),
(r'^articles/(\d{4})/(\d{2})/(\d+)/$', 'news.views.article_detail'),
)
Notes:
* ``from django.conf.urls.defaults import *`` makes the ``patterns()``
function available.
* To capture a value from the URL, just put parenthesis around it.
* There's no need to add a leading slash, because every URL has that. For
example, it's ``^articles``, not ``^/articles``.
* The ``'r'`` in front of each regular expression string is optional but
recommended. It tells Python that a string is "raw" -- that nothing in
the string should be escaped. See `Dive Into Python's explanation`_.
Example requests:
* A request to ``/articles/2005/03/`` would match the third entry in the
list. Django would call the function
``news.views.month_archive(request, '2005', '03')``.
* ``/articles/2005/3/`` would not match any URL patterns, because the
third entry in the list requires two digits for the month.
* ``/articles/2003/`` would match the first pattern in the list, not the
second one, because the patterns are tested in order, and the first one
is the first test to pass. Feel free to exploit the ordering to insert
special cases like this.
* ``/articles/2003`` would not match any of these patterns, because each
pattern requires that the URL end with a slash.
* ``/articles/2003/03/03/`` would match the final pattern. Django would call
the function ``news.views.article_detail(request, '2003', '03', '03')``.
.. _Dive Into Python's explanation: http://diveintopython.org/regular_expressions/street_addresses.html#re.matching.2.3
Named groups
============
The above example used simple, *non-named* regular-expression groups (via
parenthesis) to capture bits of the URL and pass them as *positional* arguments
to a view. In more advanced usage, it's possible to use *named*
regular-expression groups to capture URL bits and pass them as *keyword*
arguments to a view.
In Python regular expressions, the syntax for named regular-expression groups
is ``(?P<name>pattern)``, where ``name`` is the name of the group and
``pattern`` is some pattern to match.
Here's the above example URLconf, rewritten to use named groups::
urlpatterns = patterns('',
(r'^articles/2003/$', 'news.views.special_case_2003'),
(r'^articles/(?P<year>\d{4})/$', 'news.views.year_archive'),
(r'^articles/(?P<year>\d{4})/(?P<month>\d{2})/$', 'news.views.month_archive'),
(r'^articles/(?P<year>\d{4})/(?P<month>\d{2})/(?P<day>\d{2})/$', 'news.views.article_detail'),
)
This accomplishes exactly the same thing as the previous example, with one
subtle difference: The captured values are passed to view functions as keyword
arguments rather than positional arguments. For example:
* A request to ``/articles/2005/03/`` would call the function
``news.views.month_archive(request, year='2005', month='03')``, instead
of ``news.views.month_archive(request, '2005', '03')``.
* A request to ``/articles/2003/03/03/`` would call the function
``news.views.article_detail(request, year='2003', month='03', day='03')``.
In practice, this means your URLconfs are slightly more explicit and less prone
to argument-order bugs -- and you can reorder the arguments in your views'
function definitions. Of course, these benefits come at the cost of brevity;
some developers find the named-group syntax ugly and too verbose.
The matching/grouping algorithm
-------------------------------
Here's the algorithm the URLconf parser follows, with respect to named groups
vs. non-named groups in a regular expression:
If there are any named arguments, it will use those, ignoring non-named arguments.
Otherwise, it will pass all non-named arguments as positional arguments.
In both cases, it will pass any extra keyword arguments as keyword arguments.
See "Passing extra options to view functions" below.
What the URLconf searches against
=================================
The URLconf searches against the requested URL, as a normal Python string. This
does not include GET or POST parameters, or the domain name.
For example, in a request to ``http://www.example.com/myapp/``, the URLconf
will look for ``myapp/``.
In a request to ``http://www.example.com/myapp/?page=3``, the URLconf will look
for ``myapp/``.
The URLconf doesn't look at the request method. In other words, all request
methods -- ``POST``, ``GET``, ``HEAD``, etc. -- will be routed to the same
function for the same URL.
Syntax of the urlpatterns variable
==================================
``urlpatterns`` should be a Python list, in the format returned by the function
:func:`django.conf.urls.defaults.patterns`. Always use ``patterns()`` to create
the ``urlpatterns`` variable.
Convention is to use ``from django.conf.urls.defaults import *`` at the top of
your URLconf. This gives your module access to these objects:
.. module:: django.conf.urls.defaults
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
`The view prefix`_ below.
The remaining arguments should be tuples in this format::
(regular expression, Python callback function [, optional dictionary [, optional name]])
...where ``optional dictionary`` and ``optional name`` are optional. (See
`Passing extra options to view functions`_ below.)
.. 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 `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 `Including other URLconfs`_ below.
Error handling
==============
When Django can't find a regex matching the requested URL, or when an
exception is raised, Django will invoke an error-handling view. The
views to use for these cases are specified by two variables which can
be set in your root URLconf. Setting these variables in any other
URLconf will have no effect.
See the documentation on :ref:`customizing error views
<customizing-error-views>` for more details.
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.
.. versionchanged:: 1.2
Previous versions of Django only accepted strings representing import paths.
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.
.. versionchanged:: 1.2
Previous versions of Django only accepted strings representing import paths.
Notes on capturing text in URLs
===============================
Each captured argument is sent to the view as a plain Python string, regardless
of what sort of match the regular expression makes. For example, in this
URLconf line::
(r'^articles/(?P<year>\d{4})/$', 'news.views.year_archive'),
...the ``year`` argument to ``news.views.year_archive()`` will be a string, not
an integer, even though the ``\d{4}`` will only match integer strings.
A convenient trick is to specify default parameters for your views' arguments.
Here's an example URLconf and view::
# URLconf
urlpatterns = patterns('',
(r'^blog/$', 'blog.views.page'),
(r'^blog/page(?P<num>\d+)/$', 'blog.views.page'),
)
# View (in blog/views.py)
def page(request, num="1"):
# Output the appropriate page of blog entries, according to num.
In the above example, both URL patterns point to the same view --
``blog.views.page`` -- but the first pattern doesn't capture anything from the
URL. If the first pattern matches, the ``page()`` function will use its
default argument for ``num``, ``"1"``. If the second pattern matches,
``page()`` will use whatever ``num`` value was captured by the regex.
Performance
===========
Each regular expression in a ``urlpatterns`` is compiled the first time it's
accessed. This makes the system blazingly fast.
The view prefix
===============
You can specify a common prefix in your ``patterns()`` call, to cut down on
code duplication.
Here's the example URLconf from the :doc:`Django overview </intro/overview>`::
from django.conf.urls.defaults import *
urlpatterns = patterns('',
(r'^articles/(\d{4})/$', 'news.views.year_archive'),
(r'^articles/(\d{4})/(\d{2})/$', 'news.views.month_archive'),
(r'^articles/(\d{4})/(\d{2})/(\d+)/$', 'news.views.article_detail'),
)
In this example, each view has a common prefix -- ``'news.views'``.
Instead of typing that out for each entry in ``urlpatterns``, you can use the
first argument to the ``patterns()`` function to specify a prefix to apply to
each view function.
With this in mind, the above example can be written more concisely as::
from django.conf.urls.defaults import *
urlpatterns = patterns('news.views',
(r'^articles/(\d{4})/$', 'year_archive'),
(r'^articles/(\d{4})/(\d{2})/$', 'month_archive'),
(r'^articles/(\d{4})/(\d{2})/(\d+)/$', 'article_detail'),
)
Note that you don't put a trailing dot (``"."``) in the prefix. Django puts
that in automatically.
Multiple view prefixes
----------------------
In practice, you'll probably end up mixing and matching views to the point
where the views in your ``urlpatterns`` won't have a common prefix. However,
you can still take advantage of the view prefix shortcut to remove duplication.
Just add multiple ``patterns()`` objects together, like this:
Old::
from django.conf.urls.defaults import *
urlpatterns = patterns('',
(r'^$', 'django.views.generic.date_based.archive_index'),
(r'^(?P<year>\d{4})/(?P<month>[a-z]{3})/$', 'django.views.generic.date_based.archive_month'),
(r'^tag/(?P<tag>\w+)/$', 'weblog.views.tag'),
)
New::
from django.conf.urls.defaults import *
urlpatterns = patterns('django.views.generic.date_based',
(r'^$', 'archive_index'),
(r'^(?P<year>\d{4})/(?P<month>[a-z]{3})/$','archive_month'),
)
urlpatterns += patterns('weblog.views',
(r'^tag/(?P<tag>\w+)/$', 'tag'),
)
Including other URLconfs
========================
At any point, your ``urlpatterns`` can "include" other URLconf modules. This
essentially "roots" a set of URLs below other ones.
For example, here's the URLconf for the `Django Web site`_ itself. It includes a
number of other URLconfs::
from django.conf.urls.defaults import *
urlpatterns = patterns('',
(r'^weblog/', include('django_website.apps.blog.urls.blog')),
(r'^documentation/', include('django_website.apps.docs.urls.docs')),
(r'^comments/', include('django.contrib.comments.urls')),
)
Note that the regular expressions in this example don't have a ``$``
(end-of-string match character) but do include a trailing slash. Whenever
Django encounters ``include()``, it chops off whatever part of the URL matched
up to that point and sends the remaining string to the included URLconf for
further processing.
Another possibility is to include additional URL patterns not by specifying the
URLconf Python module defining them as the `include`_ argument but by using
directly the pattern list as returned by `patterns`_ instead. For example::
from django.conf.urls.defaults import *
extra_patterns = patterns('',
url(r'^reports/(?P<id>\d+)/$', 'credit.views.report', name='credit-reports'),
url(r'^charge/$', 'credit.views.charge', name='credit-charge'),
)
urlpatterns = patterns('',
url(r'^$', 'apps.main.views.homepage', name='site-homepage'),
(r'^help/', include('apps.help.urls')),
(r'^credit/', include(extra_patterns)),
)
This approach can be seen in use when you deploy an instance of the Django
Admin application. The Django Admin is deployed as instances of a
:class:`~django.contrib.admin.AdminSite`; each
:class:`~django.contrib.admin.AdminSite` instance has an attribute ``urls``
that returns the url patterns available to that instance. It is this attribute
that you ``include()`` into your projects ``urlpatterns`` when you deploy the
admin instance.
.. _`Django Web site`: http://www.djangoproject.com/
Captured parameters
-------------------
An included URLconf receives any captured parameters from parent URLconfs, so
the following example is valid::
# In settings/urls/main.py
urlpatterns = patterns('',
(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})/$', 'year_archive', {'foo': 'bar'}),
)
In this example, for a request to ``/blog/2005/``, Django will call the
``blog.views.year_archive()`` view, passing it these keyword arguments::
year='2005', foo='bar'
This technique is used in :doc:`generic views </ref/generic-views>` and in the
:doc:`syndication framework </ref/contrib/syndication>` to pass metadata and
options to views.
.. admonition:: Dealing with conflicts
It's possible to have a URL pattern which captures named keyword arguments,
and also passes arguments with the same names in its dictionary of extra
arguments. When this happens, the arguments in the dictionary will be used
instead of the arguments captured in the URL.
Passing extra options to ``include()``
--------------------------------------
Similarly, you can pass extra options to ``include()``. When you pass extra
options to ``include()``, *each* line in the included URLconf will be passed
the extra options.
For example, these two URLconf sets are functionally identical:
Set one::
# main.py
urlpatterns = patterns('',
(r'^blog/', include('inner'), {'blogid': 3}),
)
# inner.py
urlpatterns = patterns('',
(r'^archive/$', '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*
URLpatterns 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``.
Utility methods
===============
.. 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 method (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>`.
.. 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 ouput of :meth:`~django.core.urlresolvers.reverse`
may produce undesirable results.
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 testing if 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 ``"/"``, but it can be
changed, for instance by using ``django.root`` (see :doc:`How to use
Django with Apache and mod_python </howto/deployment/modpython>`).