old_contents: from django.http import HttpResponse
  from django.template import RequestContext, loader
  from polls.models import Question
  from django.shortcuts import get_object_or_404, render
  from django.http import Http404
  
  
  def index(request):
      latest_question_list = Question.objects.order_by('-pub_date')[:5]
      context = {'latest_question_list': latest_question_list}
      return render(request, 'polls/index.html', context)
  
  def detail(request, question_id):
      question = get_object_or_404(Question, pk=question_id)
      return render(request, 'polls/detail.html', {'question': question})
  
  def results(request, question_id):
      response = "You're looking at the results of question %s."
      return HttpResponse(response % question_id)
  
  def vote(request, question_id):
      return HttpResponse("You're voting on question %s." % question_id)
  
  #def html(request, question_id):
  #    return HttpResponse("HTML page of %s." % question_id)
new_contents: from django.template import RequestContext, loader
  from polls.models import Question
  from django.shortcuts import get_object_or_404, render
  from django.http import Http404, HttpResponseRedirect, HttpResponse
  from django.core.urlresolvers import reverse
  
  
  def index(request):
      latest_question_list = Question.objects.order_by('-pub_date')[:5]
      context = {'latest_question_list': latest_question_list}
      return render(request, 'polls/index.html', context)
  
  def detail(request, question_id):
      question = get_object_or_404(Question, pk=question_id)
      return render(request, 'polls/detail.html', {'question': question})
  
  def results(request, question_id):
      response = "You're looking at the results of question %s."
      return HttpResponse(response % question_id)
  
  def vote(request, question_id):
      p = get_object_or_404(Question, pk=question_id)
      try:
          selected_choice = p.choice_set.get(pk=request.POST['choice'])
      except (KeyError, Choice.DoesNotExist):
          # Redisplay the question voting form.
          return render(request, 'polls/detail.html', {
              'question': p,
              'error_message': "You didn't select a choice.",
          })
      else:
          selected_choice.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=(p.id,)))
  
  #def html(request, question_id):
  #    return HttpResponse("HTML page of %s." % question_id)
subject: improve vote