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Changes between Version 3 and Version 4 of DjangoDocumentKoreanTranslation/tutorial03


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  • DjangoDocumentKoreanTranslation/tutorial03

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    1 번역중입니다. 작성중인 초안을 보시려면 [http://code.djangoproject.com/wiki/DjangoDocumentKoreanTranslation/tutorial03.txt 이곳]을 클릭하세요 
     1{{{ 
     2.. _intro-tutorial03: 
     3 
     4===================================== 
     5>>! 
     6Writing your first Django app, part 3 
     7<<! 
     8>>! 
     9세번째 : views 작성하기 
     10<<! 
     11===================================== 
     12>>! 
     13This tutorial begins where :ref:`Tutorial 2 <intro-tutorial02>` left off. We're 
     14continuing the Web-poll application and will focus on creating the public 
     15interface -- "views." 
     16<<! 
     17>>! 
     18이 페이지는 "views"라는 public interface에 대해 중점을 두고 Web-poll 어플리케이션을 다룹니다. 
     19<<! 
     20>>! 
     21Philosophy 
     22<<! 
     23>>! 
     24개념 
     25<<! 
     26========== 
     27>>! 
     28A view is a "type" of Web page in your Django application that generally serves 
     29a specific function and has a specific template. For example, in a weblog 
     30application, you might have the following views: 
     31<<! 
     32>>! 
     33뷰(view)는 장고 어플리케이션에서 구체적인 기능을 수행하고, 특정한 템플릿을 가지고 있기도 한 웹페이지의 "형태"중 한가지 입니다. 예를들어, 만약 당신이 블로그 어플리케이션을 만든다면, 아래와 같은 뷰를 사용해야 할 것입니다. 
     34<<! 
     35>>! 
     36    * Blog homepage -- displays the latest few entries. 
     37 
     38    * Entry "detail" page -- permalink page for a single entry. 
     39 
     40    * Year-based archive page -- displays all months with entries in the 
     41      given year. 
     42 
     43    * Month-based archive page -- displays all days with entries in the 
     44      given month. 
     45 
     46    * Day-based archive page -- displays all entries in the given day. 
     47 
     48    * Comment action -- handles posting comments to a given entry. 
     49<<! 
     50>>! 
     51    * 블로그 홈페이지 -- 최근에 올라온 글 몇개를 보여줍니다. 
     52 
     53    * 글 "자세히" 페이지 -- 한 개의 글에 대한 바로 가기 페이지 
     54 
     55    * 1년 기준 문서 페이지 -- 1년 동안의 모든 글을 보여줍니다. 
     56 
     57    * 한달 기준 문서 페이지 -- 한달 동안의 모든 글을 보여줍니다. 
     58 
     59    * 하루 기준 문서 페이지 -- 하루 동안의 모든 글을 보여줍니다. 
     60 
     61    * 댓글 처리 -- 글에 대한 댓글을 작성하는 작업을 합니다. 
     62<<! 
     63>>! 
     64In our poll application, we'll have the following four views: 
     65<<! 
     66>>! 
     67우리의 poll 어플리케이션에서는 아래의 네가지 뷰를 쓸 것 입니다. 
     68<<! 
     69>>! 
     70    * Poll "archive" page -- displays the latest few polls. 
     71 
     72    * Poll "detail" page -- displays a poll question, with no results but 
     73      with a form to vote. 
     74 
     75    * Poll "results" page -- displays results for a particular poll. 
     76 
     77    * Vote action -- handles voting for a particular choice in a particular 
     78      poll. 
     79<<! 
     80>>! 
     81    * Poll "문서" 페이지 -- 최근 몇개의 poll들을 보여줍니다. 
     82 
     83    * Poll "자세히" 페이지 -- poll의 제목과, 투표를 하기위한 폼을 보여줍니다. (결과는 없음) 
     84 
     85    * Poll "결과" 페이지 -- 특정한 poll의 결과를 보여줍니다. 
     86 
     87    * 투표 처리 -- 특정한 poll에 대한 특정한 선택에 대한 투표를 처리합니다. 
     88<<! 
     89>>! 
     90In Django, each view is represented by a simple Python function. 
     91<<! 
     92>>! 
     93장고에서 각각의 뷰는 간단한 파이썬 함수로 만들 수 있습니다. 
     94<<! 
     95>>! 
     96Design your URLs 
     97<<! 
     98>>! 
     99URL 디자인 하기 
     100<<! 
     101================ 
     102>>! 
     103The first step of writing views is to design your URL structure. You do this by 
     104creating a Python module, called a URLconf. URLconfs are how Django associates 
     105a given URL with given Python code. 
     106<<! 
     107>>! 
     108뷰를 작성하기 위한 첫 번째 단계는 URLconf라는 파이썬 모듈을 작성해서 URL 구조를 설계하는 것입니다. 
     109URLconf는 특정 URL을 그에 주어진 파이썬 코드로 연결시킵니다. 
     110<<! 
     111>>! 
     112When a user requests a Django-powered page, the system looks at the 
     113:setting:`ROOT_URLCONF` setting, which contains a string in Python dotted 
     114syntax. Django loads that module and looks for a module-level variable called 
     115``urlpatterns``, which is a sequence of tuples in the following format:: 
     116<<! 
     117>>!  
     118유저가 장고기반 페이지를 요청하면 시스템은 Python dotted 문법의 문자열을 포함한 :setting:`ROOT_URLCONF` 세팅을 불러들이고, 
     119아래와 같은 튜플 형태인 ``urlpatterns`` 라는 모듈레벨의 변수를 찾습니다.:: 
     120<<! 
     121>>! 
     122    (regular expression, Python callback function [, optional dictionary]) 
     123<<! 
     124>>! 
     125    (정규표현식, 파이썬 콜백 함수, [, 부가적인 사전자료형]) 
     126<<! 
     127>>! 
     128Django starts at the first regular expression and makes its way down the list, 
     129comparing the requested URL against each regular expression until it finds one 
     130that matches. 
     131<<! 
     132>>! 
     133장고는 요청된 URL을 나타내는 정규표현식이 나올 때 까지 첫 번째 정규표현식부터 아래로 쭉 훑습니다. 
     134<<! 
     135>>! 
     136When it finds a match, Django calls the Python callback function, with an 
     137:class:`~django.http.HttpRequest` object as the first argument, any "captured" 
     138values from the regular expression as keyword arguments, and, optionally, 
     139arbitrary keyword arguments from the dictionary (an optional third item in the 
     140tuple). 
     141<<! 
     142>>! 
     143적합한 정규표현식을 찾았다면, 장고는 :class:`~django.http.HttpRequest`를 첫번째 인자로 하는 파이썬 콜백 함수를 호출합니다. 
     144정규표현식에 의해 "걸려진" 값들도 키워드 인자로 전달되고, 위의 사전자료형 (세번째로 받은 튜플값)에서도 인자가 전달됩니다. 
     145<<! 
     146>>! 
     147For more on :class:`~django.http.HttpRequest` objects, see the 
     148:ref:`ref-request-response`. For more details on URLconfs, see the 
     149:ref:`topics-http-urls`. 
     150<<! 
     151>>! 
     152:class:`~django.http.HttpRequest`에 대한 더 많은정보는 :ref:`ref-request-response`이곳에서, URLconfs에 관한 정보는 :ref:`topics-http-urls`이 곳을 참고 하세요 
     153<<! 
     154>>! 
     155When you ran ``django-admin.py startproject mysite`` at the beginning of 
     156Tutorial 1, it created a default URLconf in ``mysite/urls.py``. It also 
     157automatically set your :setting:`ROOT_URLCONF` setting (in ``settings.py``) to 
     158point at that file:: 
     159<<! 
     160>>! 
     161만약 여러분이 튜토리얼1 에서 ``django-admin.py startproject mysite`` 커맨드를 실행하셨다면 URLconf가 ``mysite/urls.py``에 기본적으로 생겼을 것이고, 
     162:setting:`ROOT_URLCONF`세팅또한 ``setting.py``에 생겼을 것입니다.:: 
     163<<! 
     164    ROOT_URLCONF = 'mysite.urls' 
     165>>! 
     166Time for an example. Edit ``mysite/urls.py`` so it looks like this:: 
     167<<! 
     168>>! 
     169이제 예를들기위해 ``mysite/urls.py`` 를 수정해보겠습니다. 대략 아래와 같이 생겼습니다:: 
     170<<! 
     171    from django.conf.urls.defaults import * 
     172 
     173    from django.contrib import admin 
     174    admin.autodiscover() 
     175 
     176    urlpatterns = patterns('', 
     177        (r'^polls/$', 'mysite.polls.views.index'), 
     178        (r'^polls/(?P<poll_id>\d+)/$', 'mysite.polls.views.detail'), 
     179        (r'^polls/(?P<poll_id>\d+)/results/$', 'mysite.polls.views.results'), 
     180        (r'^polls/(?P<poll_id>\d+)/vote/$', 'mysite.polls.views.vote'), 
     181        (r'^admin/', include(admin.site.urls)), 
     182    ) 
     183>>! 
     184This is worth a review. When somebody requests a page from your Web site -- say, 
     185"/polls/23/", Django will load this Python module, because it's pointed to by 
     186the :setting:`ROOT_URLCONF` setting. It finds the variable named ``urlpatterns`` 
     187and traverses the regular expressions in order. When it finds a regular 
     188expression that matches -- ``r'^polls/(?P<poll_id>\d+)/$'`` -- it loads the 
     189function ``detail()`` from ``mysite/polls/views.py``. Finally, 
     190it calls that ``detail()`` function like so:: 
     191<<! 
     192 
     193    detail(request=<HttpRequest object>, poll_id='23') 
     194 
     195The ``poll_id='23'`` part comes from ``(?P<poll_id>\d+)``. Using parenthesis 
     196around a pattern "captures" the text matched by that pattern and sends it as an 
     197argument to the view function; the ``?P<poll_id>`` defines the name that will be 
     198used to identify the matched pattern; and ``\d+`` is a regular expression to 
     199match a sequence of digits (i.e., a number). 
     200 
     201Because the URL patterns are regular expressions, there really is no limit on 
     202what you can do with them. And there's no need to add URL cruft such as ``.php`` 
     203-- unless you have a sick sense of humor, in which case you can do something 
     204like this:: 
     205 
     206    (r'^polls/latest\.php$', 'mysite.polls.views.index'), 
     207 
     208But, don't do that. It's silly. 
     209 
     210Note that these regular expressions do not search GET and POST parameters, or 
     211the domain name. For example, in a request to ``http://www.example.com/myapp/``, 
     212the URLconf will look for ``myapp/``. In a request to 
     213``http://www.example.com/myapp/?page=3``, the URLconf will look for ``myapp/``. 
     214 
     215If you need help with regular expressions, see `Wikipedia's entry`_ and the 
     216`Python documentation`_. Also, the O'Reilly book "Mastering Regular Expressions" 
     217by Jeffrey Friedl is fantastic. 
     218 
     219Finally, a performance note: these regular expressions are compiled the first 
     220time the URLconf module is loaded. They're super fast. 
     221 
     222.. _Wikipedia's entry: http://en.wikipedia.org/wiki/Regular_expression 
     223.. _Python documentation: http://docs.python.org/library/re.html 
     224 
     225Write your first view 
     226===================== 
     227 
     228Well, we haven't created any views yet -- we just have the URLconf. But let's 
     229make sure Django is following the URLconf properly. 
     230 
     231Fire up the Django development Web server: 
     232 
     233.. code-block:: bash 
     234 
     235    python manage.py runserver 
     236 
     237Now go to "http://localhost:8000/polls/" on your domain in your Web browser. 
     238You should get a pleasantly-colored error page with the following message:: 
     239 
     240    ViewDoesNotExist at /polls/ 
     241 
     242    Tried index in module mysite.polls.views. Error was: 'module' 
     243    object has no attribute 'index' 
     244 
     245This error happened because you haven't written a function ``index()`` in the 
     246module ``mysite/polls/views.py``. 
     247 
     248Try "/polls/23/", "/polls/23/results/" and "/polls/23/vote/". The error 
     249messages tell you which view Django tried (and failed to find, because you 
     250haven't written any views yet). 
     251 
     252Time to write the first view. Open the file ``mysite/polls/views.py`` 
     253and put the following Python code in it:: 
     254 
     255    from django.http import HttpResponse 
     256 
     257    def index(request): 
     258        return HttpResponse("Hello, world. You're at the poll index.") 
     259 
     260This is the simplest view possible. Go to "/polls/" in your browser, and you 
     261should see your text. 
     262 
     263Now lets add a few more views. These views are slightly different, because 
     264they take an argument (which, remember, is passed in from whatever was 
     265captured by the regular expression in the URLconf):: 
     266 
     267    def detail(request, poll_id): 
     268        return HttpResponse("You're looking at poll %s." % poll_id) 
     269 
     270    def results(request, poll_id): 
     271        return HttpResponse("You're looking at the results of poll %s." % poll_id) 
     272 
     273    def vote(request, poll_id): 
     274        return HttpResponse("You're voting on poll %s." % poll_id) 
     275 
     276Take a look in your browser, at "/polls/34/". It'll run the `detail()` method 
     277and display whatever ID you provide in the URL. Try "/polls/34/results/" and 
     278"/polls/34/vote/" too -- these will display the placeholder results and voting 
     279pages. 
     280 
     281Write views that actually do something 
     282====================================== 
     283 
     284Each view is responsible for doing one of two things: Returning an 
     285:class:`~django.http.HttpResponse` object containing the content for the 
     286requested page, or raising an exception such as :exc:`~django.http.Http404`. The 
     287rest is up to you. 
     288 
     289Your view can read records from a database, or not. It can use a template 
     290system such as Django's -- or a third-party Python template system -- or not. 
     291It can generate a PDF file, output XML, create a ZIP file on the fly, anything 
     292you want, using whatever Python libraries you want. 
     293 
     294All Django wants is that :class:`~django.http.HttpResponse`. Or an exception. 
     295 
     296Because it's convenient, let's use Django's own database API, which we covered 
     297in :ref:`Tutorial 1 <intro-tutorial01>`. Here's one stab at the ``index()`` 
     298view, which displays the latest 5 poll questions in the system, separated by 
     299commas, according to publication date:: 
     300 
     301    from mysite.polls.models import Poll 
     302    from django.http import HttpResponse 
     303 
     304    def index(request): 
     305        latest_poll_list = Poll.objects.all().order_by('-pub_date')[:5] 
     306        output = ', '.join([p.question for p in latest_poll_list]) 
     307        return HttpResponse(output) 
     308 
     309There's a problem here, though: The page's design is hard-coded in the view. If 
     310you want to change the way the page looks, you'll have to edit this Python code. 
     311So let's use Django's template system to separate the design from Python:: 
     312 
     313    from django.template import Context, loader 
     314    from mysite.polls.models import Poll 
     315    from django.http import HttpResponse 
     316 
     317    def index(request): 
     318        latest_poll_list = Poll.objects.all().order_by('-pub_date')[:5] 
     319        t = loader.get_template('polls/index.html') 
     320        c = Context({ 
     321            'latest_poll_list': latest_poll_list, 
     322        }) 
     323        return HttpResponse(t.render(c)) 
     324 
     325That code loads the template called "polls/index.html" and passes it a context. 
     326The context is a dictionary mapping template variable names to Python objects. 
     327 
     328Reload the page. Now you'll see an error:: 
     329 
     330    TemplateDoesNotExist at /polls/ 
     331    polls/index.html 
     332 
     333Ah. There's no template yet. First, create a directory, somewhere on your 
     334filesystem, whose contents Django can access. (Django runs as whatever user your 
     335server runs.) Don't put them under your document root, though. You probably 
     336shouldn't make them public, just for security's sake. 
     337Then edit :setting:`TEMPLATE_DIRS` in your ``settings.py`` to tell Django where 
     338it can find templates -- just as you did in the "Customize the admin look and 
     339feel" section of Tutorial 2. 
     340 
     341When you've done that, create a directory ``polls`` in your template directory. 
     342Within that, create a file called ``index.html``. Note that our 
     343``loader.get_template('polls/index.html')`` code from above maps to 
     344"[template_directory]/polls/index.html" on the filesystem. 
     345 
     346Put the following code in that template: 
     347 
     348.. code-block:: html+django 
     349 
     350    {% if latest_poll_list %} 
     351        <ul> 
     352        {% for poll in latest_poll_list %} 
     353            <li>{{ poll.question }}</li> 
     354        {% endfor %} 
     355        </ul> 
     356    {% else %} 
     357        <p>No polls are available.</p> 
     358    {% endif %} 
     359 
     360Load the page in your Web browser, and you should see a bulleted-list 
     361containing the "What's up" poll from Tutorial 1. 
     362 
     363A shortcut: render_to_response() 
     364-------------------------------- 
     365 
     366It's a very common idiom to load a template, fill a context and return an 
     367:class:`~django.http.HttpResponse` object with the result of the rendered 
     368template. Django provides a shortcut. Here's the full ``index()`` view, 
     369rewritten:: 
     370 
     371    from django.shortcuts import render_to_response 
     372    from mysite.polls.models import Poll 
     373 
     374    def index(request): 
     375        latest_poll_list = Poll.objects.all().order_by('-pub_date')[:5] 
     376        return render_to_response('polls/index.html', {'latest_poll_list': latest_poll_list}) 
     377 
     378Note that once we've done this in all these views, we no longer need to import 
     379:mod:`~django.template.loader`, :class:`~django.template.Context` and 
     380:class:`~django.http.HttpResponse`. 
     381 
     382The :func:`~django.shortcuts.render_to_response` function takes a template name 
     383as its first argument and a dictionary as its optional second argument. It 
     384returns an :class:`~django.http.HttpResponse` object of the given template 
     385rendered with the given context. 
     386 
     387Raising 404 
     388=========== 
     389 
     390Now, let's tackle the poll detail view -- the page that displays the question 
     391for a given poll. Here's the view:: 
     392 
     393    from django.http import Http404 
     394    # ... 
     395    def detail(request, poll_id): 
     396        try: 
     397            p = Poll.objects.get(pk=poll_id) 
     398        except Poll.DoesNotExist: 
     399            raise Http404 
     400        return render_to_response('polls/detail.html', {'poll': p}) 
     401 
     402The new concept here: The view raises the :exc:`~django.http.Http404` exception 
     403if a poll with the requested ID doesn't exist. 
     404 
     405We'll discuss what you could put in that ``polls/detail.html`` template a bit 
     406later, but if you'd like to quickly get the above example working, just:: 
     407 
     408    {{ poll }} 
     409 
     410will get you started for now. 
     411 
     412A shortcut: get_object_or_404() 
     413------------------------------- 
     414 
     415It's a very common idiom to use :meth:`~django.db.models.QuerySet.get` and raise 
     416:exc:`~django.http.Http404` if the object doesn't exist. Django provides a 
     417shortcut. Here's the ``detail()`` view, rewritten:: 
     418 
     419    from django.shortcuts import render_to_response, get_object_or_404 
     420    # ... 
     421    def detail(request, poll_id): 
     422        p = get_object_or_404(Poll, pk=poll_id) 
     423        return render_to_response('polls/detail.html', {'poll': p}) 
     424 
     425The :func:`~django.shortcuts.get_object_or_404` function takes a Django model 
     426as its first argument and an arbitrary number of keyword arguments, which it 
     427passes to the module's :meth:`~django.db.models.QuerySet.get` function. It 
     428raises :exc:`~django.http.Http404` if the object doesn't exist. 
     429 
     430.. admonition:: Philosophy 
     431 
     432    Why do we use a helper function :func:`~django.shortcuts.get_object_or_404` 
     433    instead of automatically catching the 
     434    :exc:`~django.core.exceptions.ObjectDoesNotExist` exceptions at a higher 
     435    level, or having the model API raise :exc:`~django.http.Http404` instead of 
     436    :exc:`~django.core.exceptions.ObjectDoesNotExist`? 
     437 
     438    Because that would couple the model layer to the view layer. One of the 
     439    foremost design goals of Django is to maintain loose coupling. 
     440 
     441There's also a :func:`~django.shortcuts.get_list_or_404` function, which works 
     442just as :func:`~django.shortcuts.get_object_or_404` -- except using 
     443:meth:`~django.db.models.QuerySet.filter` instead of 
     444:meth:`~django.db.models.QuerySet.get`. It raises :exc:`~django.http.Http404` if 
     445the list is empty. 
     446 
     447Write a 404 (page not found) view 
     448================================= 
     449 
     450When you raise :exc:`~django.http.Http404` from within a view, Django will load 
     451a special view devoted to handling 404 errors. It finds it by looking for the 
     452variable ``handler404``, which is a string in Python dotted syntax -- the same 
     453format the normal URLconf callbacks use. A 404 view itself has nothing special: 
     454It's just a normal view. 
     455 
     456You normally won't have to bother with writing 404 views. By default, URLconfs 
     457have the following line up top:: 
     458 
     459    from django.conf.urls.defaults import * 
     460 
     461That takes care of setting ``handler404`` in the current module. As you can see 
     462in ``django/conf/urls/defaults.py``, ``handler404`` is set to 
     463:func:`django.views.defaults.page_not_found` by default. 
     464 
     465Four more things to note about 404 views: 
     466 
     467    * If :setting:`DEBUG` is set to ``True`` (in your settings module) then your 
     468      404 view will never be used (and thus the ``404.html`` template will never 
     469      be rendered) because the traceback will be displayed instead. 
     470 
     471    * The 404 view is also called if Django doesn't find a match after checking 
     472      every regular expression in the URLconf. 
     473 
     474    * If you don't define your own 404 view -- and simply use the default, which 
     475      is recommended -- you still have one obligation: To create a ``404.html`` 
     476      template in the root of your template directory. The default 404 view will 
     477      use that template for all 404 errors. 
     478 
     479    * If :setting:`DEBUG` is set to ``False`` (in your settings module) and if 
     480      you didn't create a ``404.html`` file, an ``Http500`` is raised instead. 
     481      So remember to create a ``404.html``. 
     482 
     483Write a 500 (server error) view 
     484=============================== 
     485 
     486Similarly, URLconfs may define a ``handler500``, which points to a view to call 
     487in case of server errors. Server errors happen when you have runtime errors in 
     488view code. 
     489 
     490Use the template system 
     491======================= 
     492 
     493Back to the ``detail()`` view for our poll application. Given the context 
     494variable ``poll``, here's what the "polls/detail.html" template might look 
     495like: 
     496 
     497.. code-block:: html+django 
     498 
     499    <h1>{{ poll.question }}</h1> 
     500    <ul> 
     501    {% for choice in poll.choice_set.all %} 
     502        <li>{{ choice.choice }}</li> 
     503    {% endfor %} 
     504    </ul> 
     505 
     506The template system uses dot-lookup syntax to access variable attributes. In 
     507the example of ``{{ poll.question }}``, first Django does a dictionary lookup 
     508on the object ``poll``. Failing that, it tries attribute lookup -- which works, 
     509in this case. If attribute lookup had failed, it would've tried calling the 
     510method ``question()`` on the poll object. 
     511 
     512Method-calling happens in the ``{% for %}`` loop: ``poll.choice_set.all`` is 
     513interpreted as the Python code ``poll.choice_set.all()``, which returns an 
     514iterable of Choice objects and is suitable for use in the ``{% for %}`` tag. 
     515 
     516See the :ref:`template guide <topics-templates>` for more about templates. 
     517 
     518Simplifying the URLconfs 
     519======================== 
     520 
     521Take some time to play around with the views and template system. As you edit 
     522the URLconf, you may notice there's a fair bit of redundancy in it:: 
     523 
     524    urlpatterns = patterns('', 
     525        (r'^polls/$', 'mysite.polls.views.index'), 
     526        (r'^polls/(?P<poll_id>\d+)/$', 'mysite.polls.views.detail'), 
     527        (r'^polls/(?P<poll_id>\d+)/results/$', 'mysite.polls.views.results'), 
     528        (r'^polls/(?P<poll_id>\d+)/vote/$', 'mysite.polls.views.vote'), 
     529    ) 
     530 
     531Namely, ``mysite.polls.views`` is in every callback. 
     532 
     533Because this is a common case, the URLconf framework provides a shortcut for 
     534common prefixes. You can factor out the common prefixes and add them as the 
     535first argument to :func:`~django.conf.urls.defaults.patterns`, like so:: 
     536 
     537    urlpatterns = patterns('mysite.polls.views', 
     538        (r'^polls/$', 'index'), 
     539        (r'^polls/(?P<poll_id>\d+)/$', 'detail'), 
     540        (r'^polls/(?P<poll_id>\d+)/results/$', 'results'), 
     541        (r'^polls/(?P<poll_id>\d+)/vote/$', 'vote'), 
     542    ) 
     543 
     544This is functionally identical to the previous formatting. It's just a bit 
     545tidier. 
     546 
     547Decoupling the URLconfs 
     548======================= 
     549 
     550While we're at it, we should take the time to decouple our poll-app URLs from 
     551our Django project configuration. Django apps are meant to be pluggable -- that 
     552is, each particular app should be transferable to another Django installation 
     553with minimal fuss. 
     554 
     555Our poll app is pretty decoupled at this point, thanks to the strict directory 
     556structure that ``python manage.py startapp`` created, but one part of it is 
     557coupled to the Django settings: The URLconf. 
     558 
     559We've been editing the URLs in ``mysite/urls.py``, but the URL design of an 
     560app is specific to the app, not to the Django installation -- so let's move the 
     561URLs within the app directory. 
     562 
     563Copy the file ``mysite/urls.py`` to ``mysite/polls/urls.py``. Then, change 
     564``mysite/urls.py`` to remove the poll-specific URLs and insert an 
     565:func:`~django.conf.urls.defaults.include`:: 
     566 
     567    # ... 
     568    urlpatterns = patterns('', 
     569        (r'^polls/', include('mysite.polls.urls')), 
     570        # ... 
     571 
     572:func:`~django.conf.urls.defaults.include`, simply, references another URLconf. 
     573Note that the regular expression doesn't have a ``$`` (end-of-string match 
     574character) but has the trailing slash. Whenever Django encounters 
     575:func:`~django.conf.urls.defaults.include`, it chops off whatever part of the 
     576URL matched up to that point and sends the remaining string to the included 
     577URLconf for further processing. 
     578 
     579Here's what happens if a user goes to "/polls/34/" in this system: 
     580 
     581    * Django will find the match at ``'^polls/'`` 
     582 
     583    * Then, Django will strip off the matching text (``"polls/"``) and send the 
     584      remaining text -- ``"34/"`` -- to the 'mysite.polls.urls' URLconf for 
     585      further processing. 
     586 
     587Now that we've decoupled that, we need to decouple the 'mysite.polls.urls' 
     588URLconf by removing the leading "polls/" from each line, and removing the 
     589lines registering the admin site:: 
     590 
     591    urlpatterns = patterns('mysite.polls.views', 
     592        (r'^$', 'index'), 
     593        (r'^(?P<poll_id>\d+)/$', 'detail'), 
     594        (r'^(?P<poll_id>\d+)/results/$', 'results'), 
     595        (r'^(?P<poll_id>\d+)/vote/$', 'vote'), 
     596    ) 
     597 
     598The idea behind :func:`~django.conf.urls.defaults.include` and URLconf 
     599decoupling is to make it easy to plug-and-play URLs. Now that polls are in their 
     600own URLconf, they can be placed under "/polls/", or under "/fun_polls/", or 
     601under "/content/polls/", or any other URL root, and the app will still work. 
     602 
     603All the poll app cares about is its relative URLs, not its absolute URLs. 
     604 
     605When you're comfortable with writing views, read :ref:`part 4 of this tutorial 
     606<intro-tutorial04>` to learn about simple form processing and generic views. 
     607}}}