Where to get help:

If you’re having trouble going through this tutorial, please head over totheGetting Help section of the FAQ.

Overview¶

A view is a “type” of web page in your Django application that generally servesa specific function and has a specific template. For example, in a blogapplication, you might have the following views:

• Blog homepage – displays the latest few entries.
• Entry “detail” page – permalink page for a single entry.
• Year-based archive page – displays all months with entries in thegiven year.
• Month-based archive page – displays all days with entries in thegiven month.
• Day-based archive page – displays all entries in the given day.
• Comment action – handles posting comments to a given entry.

In our poll application, we’ll have the following four views:

• Question “index” page – displays the latest few questions.
• Question “detail” page – displays a question text, with no results butwith a form to vote.
• Question “results” page – displays results for a particular question.
• Vote action – handles voting for a particular choice in a particularquestion.

In Django, web pages and other content are delivered by views. Each view isrepresented by a Python function (or method, in the case of class-based views).Django will choose a view by examining the URL that’s requested (to be precise,the part of the URL after the domain name).

Now in your time on the web you may have come across such beauties asME2/Sites/dirmod.htm?sid=&type=gen&mod=Core+Pages&gid=A6CD4967199A42D9B65B1B.You will be pleased to know that Django allows us much more elegantURL patterns than that.

A URL pattern is the general form of a URL - for example:/newsarchive/<year>/<month>/.

To get from a URL to a view, Django uses what are known as ‘URLconfs’. AURLconf maps URL patterns to views.

This tutorial provides basic instruction in the use of URLconfs, and you canrefer toURL dispatcher for more information.

Writing more views¶

Now let’s add a few more views topolls/views.py. These views areslightly different, because they take an argument:

defdetail(request,question_id):returnHttpResponse("You're looking at question%s."%question_id)defresults(request,question_id):response="You're looking at the results of question%s."returnHttpResponse(response%question_id)defvote(request,question_id):returnHttpResponse("You're voting on question%s."%question_id)

Wire these new views into thepolls.urls module by adding the followingpath() calls:

fromdjango.urlsimportpathfrom.importviewsurlpatterns=[# ex: /polls/path("",views.index,name="index"),# ex: /polls/5/path("<int:question_id>/",views.detail,name="detail"),# ex: /polls/5/results/path("<int:question_id>/results/",views.results,name="results"),# ex: /polls/5/vote/path("<int:question_id>/vote/",views.vote,name="vote"),]

Take a look in your browser, at “/polls/34/”. It’ll run thedetail()method and display whatever ID you provide in the URL. Try“/polls/34/results/” and “/polls/34/vote/” too – these will display theplaceholder results and voting pages.

When somebody requests a page from your website – say, “/polls/34/”, Djangowill load themysite.urls Python module because it’s pointed to by theROOT_URLCONF setting. It finds the variable namedurlpatternsand traverses the patterns in order. After finding the match at'polls/',it strips off the matching text ("polls/") and sends the remaining text –"34/" – to the ‘polls.urls’ URLconf for further processing. There itmatches'<int:question_id>/', resulting in a call to thedetail() viewlike so:

detail(request=<HttpRequest object>, question_id=34)

Thequestion_id=34 part comes from<int:question_id>. Using anglebrackets “captures” part of the URL and sends it as a keyword argument to theview function. Thequestion_id part of the string defines the name thatwill be used to identify the matched pattern, and theint part is aconverter that determines what patterns should match this part of the URL path.The colon (:) separates the converter and pattern name.

Write views that actually do something¶

Each view is responsible for doing one of two things: returning anHttpResponse object containing the content for therequested page, or raising an exception such asHttp404. Therest is up to you.

Your view can read records from a database, or not. It can use a templatesystem such as Django’s – or a third-party Python template system – or not.It can generate a PDF file, output XML, create a ZIP file on the fly, anythingyou want, using whatever Python libraries you want.

All Django wants is thatHttpResponse. Or an exception.

Because it’s convenient, let’s use Django’s own database API, which we coveredinTutorial 2. Here’s one stab at a newindex()view, which displays the latest 5 poll questions in the system, separated bycommas, according to publication date:

fromdjango.httpimportHttpResponsefrom.modelsimportQuestiondefindex(request):latest_question_list=Question.objects.order_by("-pub_date")[:5]output=", ".join([q.question_textforqinlatest_question_list])returnHttpResponse(output)# Leave the rest of the views (detail, results, vote) unchanged

There’s a problem here, though: the page’s design is hard-coded in the view. Ifyou want to change the way the page looks, you’ll have to edit this Python code.So let’s use Django’s template system to separate the design from Python bycreating a template that the view can use.

First, create a directory calledtemplates in yourpolls directory.Django will look for templates in there.

Your project’sTEMPLATES setting describes how Django will load andrender templates. The default settings file configures aDjangoTemplatesbackend whoseAPP_DIRS option is set toTrue. By conventionDjangoTemplates looks for a “templates”subdirectory in each of theINSTALLED_APPS.

Within thetemplates directory you have just created, create anotherdirectory calledpolls, and within that create a file calledindex.html. In other words, your template should be atpolls/templates/polls/index.html. Because of how theapp_directoriestemplate loader works as described above, you can refer to this template withinDjango aspolls/index.html.

Put the following code in that template:

{%iflatest_question_list%}<ul>{%forquestioninlatest_question_list%}<li><ahref="/polls/{{question.id}}/">{{question.question_text}}</a></li>{%endfor%}</ul>{%else%}<p>No polls are available.</p>{%endif%}

Now let’s update ourindex view inpolls/views.py to use the template:

fromdjango.httpimportHttpResponsefromdjango.templateimportloaderfrom.modelsimportQuestiondefindex(request):latest_question_list=Question.objects.order_by("-pub_date")[:5]template=loader.get_template("polls/index.html")context={"latest_question_list":latest_question_list,}returnHttpResponse(template.render(context,request))

That code loads the template calledpolls/index.html and passes it acontext. The context is a dictionary mapping template variable names to Pythonobjects.

Load the page by pointing your browser at “/polls/”, and you should see abulleted-list containing the “What’s up” question fromTutorial 2. The link points to the question’s detail page.

fromdjango.shortcutsimportrenderfrom.modelsimportQuestiondefindex(request):latest_question_list=Question.objects.order_by("-pub_date")[:5]context={"latest_question_list":latest_question_list}returnrender(request,"polls/index.html",context)

Raising a 404 error¶

Now, let’s tackle the question detail view – the page that displays the question textfor a given poll. Here’s the view:

fromdjango.httpimportHttp404fromdjango.shortcutsimportrenderfrom.modelsimportQuestion# ...defdetail(request,question_id):try:question=Question.objects.get(pk=question_id)exceptQuestion.DoesNotExist:raiseHttp404("Question does not exist")returnrender(request,"polls/detail.html",{"question":question})

The new concept here: The view raises theHttp404 exceptionif a question with the requested ID doesn’t exist.

We’ll discuss what you could put in thatpolls/detail.html template a bitlater, but if you’d like to quickly get the above example working, a filecontaining just:

{{question}}

will get you started for now.

fromdjango.shortcutsimportget_object_or_404,renderfrom.modelsimportQuestion# ...defdetail(request,question_id):question=get_object_or_404(Question,pk=question_id)returnrender(request,"polls/detail.html",{"question":question})

Use the template system¶

Back to thedetail() view for our poll application. Given the contextvariablequestion, here’s what thepolls/detail.html template might looklike:

<h1>{{question.question_text}}</h1><ul>{%forchoiceinquestion.choice_set.all%}<li>{{choice.choice_text}}</li>{%endfor%}</ul>

The template system uses dot-lookup syntax to access variable attributes. Inthe example of{{question.question_text}}, first Django does a dictionary lookupon the objectquestion. Failing that, it tries an attribute lookup – whichworks, in this case. If attribute lookup had failed, it would’ve tried alist-index lookup.

Method-calling happens in the{%for%} loop:question.choice_set.all is interpreted as the Python codequestion.choice_set.all(), which returns an iterable ofChoice objects and issuitable for use in the{%for%} tag.

See thetemplate guide for more about templates.

Removing hardcoded URLs in templates¶

Remember, when we wrote the link to a question in thepolls/index.htmltemplate, the link was partially hardcoded like this:

<li><ahref="/polls/{{question.id}}/">{{question.question_text}}</a></li>

The problem with this hardcoded, tightly-coupled approach is that it becomeschallenging to change URLs on projects with a lot of templates. However, sinceyou defined the name argument in thepath() functions inthepolls.urls module, you can remove a reliance on specific URL pathsdefined in your url configurations by using the{%url%} template tag:

<li><ahref="{%url'detail'question.id%}">{{question.question_text}}</a></li>

The way this works is by looking up the URL definition as specified in thepolls.urls module. You can see exactly where the URL name of ‘detail’ isdefined below:

...# the 'name' value as called by the {% url %} template tagpath("<int:question_id>/",views.detail,name="detail"),...

If you want to change the URL of the polls detail view to something else,perhaps to something likepolls/specifics/12/ instead of doing it in thetemplate (or templates) you would change it inpolls/urls.py:

...# added the word 'specifics'path("specifics/<int:question_id>/",views.detail,name="detail"),...

Namespacing URL names¶

The tutorial project has just one app,polls. In real Django projects,there might be five, ten, twenty apps or more. How does Django differentiatethe URL names between them? For example, thepolls app has adetailview, and so might an app on the same project that is for a blog. How does onemake it so that Django knows which app view to create for a url when using the{%url%} template tag?

The answer is to add namespaces to your URLconf. In thepolls/urls.pyfile, go ahead and add anapp_name to set the application namespace:

fromdjango.urlsimportpathfrom.importviewsapp_name="polls"urlpatterns=[path("",views.index,name="index"),path("<int:question_id>/",views.detail,name="detail"),path("<int:question_id>/results/",views.results,name="results"),path("<int:question_id>/vote/",views.vote,name="vote"),]

Now change yourpolls/index.html template from:

<li><ahref="{%url'detail'question.id%}">{{question.question_text}}</a></li>

to point at the namespaced detail view:

<li><ahref="{%url'polls:detail'question.id%}">{{question.question_text}}</a></li>

When you’re comfortable with writing views, readpart 4 of this tutorial to learn the basics about form processing and genericviews.