Django polls app with basics of views, url, admin and templates

 Description

  Django documentation  explains the application "polls". We illustrate the same with complete code.

Overall flow

Points to remember

• Whenever you create a form that alters data server-side, use method="post"
• In short, all POST forms that are targeted at internal URLs should use the {% csrf_token %} template tag.
• Always return an HttpResponseRedirect after successfully dealing with POST data. This prevents data from being posted twice if a user hits the Back button.
• HttpResponseRedirect takes a single argument: the URL to which the user will be redirected 

Views.py

rom django.shortcuts import render, get_object_or_404

# Create your views here.

from django.http import HttpResponse, Http404, HttpResponseRedirect
from django.template import loader
from django.urls import reverse
from .models import Question, Choice
from django.db.models import F


def index(request):
    latest_question_list = Question.objects.order_by('-pub_date')[:5]
    # output = ', '.join([q.question_text for q in latest_question_list])
    # return HttpResponse("Hello, world. You're at the polls index.")

    template = loader.get_template('polls/index.html')
    context = {
        'latest_question_list' : latest_question_list
    }
    return HttpResponse(template.render(context, request))


def detail(request, question_id):
    try:
        question = Question.objects.get(pk=question_id)
        context = { 'question' : question }
    except Question.DoesNotExist:
        raise Http404("Question does not exist")
    template = loader.get_template('polls/detail.html')
    # return HttpResponse("You're looking at question %s." % question_id)
    return HttpResponse(template.render(context, request))


def results(request, question_id):
    # response = "you are looking at the results of question %s"
    # return HttpResponse(response % question_id)
    question = get_object_or_404(Question, pk=question_id)
    return render(request, 'polls/results.html', {'question': question})


# directly calling the url from view function
def vote(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    try:
        selected_choice = question.choice_set.get(pk=request.POST['choice'])
    except (KeyError, Choice.DoesNotExist):
        # Redisplay the question voting form.
        return render(request, 'polls/detail.html', {
            'question': question,
            'error_message': "You didn't select a choice.",
        })
    else:
        selected_choice.votes = F('votes') + 1
        selected_choice.save()
        # Always return an HttpResponseRedirect after successfully dealing
        # with POST data. This prevents data from being posted twice if a
        # user hits the Back button.
        return HttpResponseRedirect(reverse('polls:results', args=(question.id,)))

Models.py

from django.db import models
from django.utils import timezone
import datetime
# Create your models here.


class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date_published')

    def __str__(self):
        return self.question_text

    def was_published_recently(self):
        return self.pub_date >= timezone.now() - datetime.timedelta(days=1)


class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

    def __str__(self):
        return self.choice_text

Urls.py

from django.urls import path

from . import views

app_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'),

]

admin.py

from django.contrib import admin

# Register your models here.

from .models import Question, Choice
admin.site.register(Question)
admin.site.register(Choice)

HTML files

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Polls</title>
  </head>
  <body>
    {% if latest_question_list %}
    <ul>
      {% for question in latest_question_list %}
      <li>
        <!-- <a href="/polls/{{ question.id }}/">{{ question.question_text }}</a> -->
        <a href="{% url 'polls:detail' question.id %}">{{ question.question_text }}</a>
      </li>
      {% endfor %}
    </ul>
    {% else %}
    <p>No polls are available.</p>
    {% endif %}
  </body>
</html>

detail.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>detail</title>
  </head>
  <body>
<form action="{% url 'polls:vote' question.id %}" method="post">
{% csrf_token %}
<fieldset>
    <legend><h1>{{ question.question_text }}</h1></legend>
    {% if error_message %}<p><strong>{{ error_message }}</strong></p>{% endif %}
    {% for choice in question.choice_set.all %}
        <input type="radio" name="choice" id="choice{{ forloop.counter }}" value="{{ choice.id }}">
        <label for="choice{{ forloop.counter }}">{{ choice.choice_text }}</label><br>
    {% endfor %}
</fieldset>
<input type="submit" value="Vote">
</form>
  </body>
</html>

results.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>results</title>
  </head>
  <body>
<h1>{{ question.question_text }}</h1>

<ul>
{% for choice in question.choice_set.all %}
    <li>{{ choice.choice_text }} -- {{ choice.votes }} vote{{ choice.votes|pluralize }}</li>
{% endfor %}
</ul>

<a href="{% url 'polls:detail' question.id %}">Vote again?</a>
  </body>
</html>