title: R Reverse for 'results' not found. 'results' is not a valid view function or pattern name
body: <p>I am learning django framework and i am getting an error "
  Reverse for 'results' not found. 'results' is not a valid view function or pattern name."
  I am including my code here.</p>
  
  <h2><code>results.py</code>:</h2>
  
  <pre><code>{% extends "polls/base.html" %}
  
  {% block main_content %}
  
  &lt;h1&gt;{{question.question_text}}&lt;/h1&gt;
  
  &lt;ul&gt;
      {% for choice in question.choice_set.all %}
          &lt;li&gt;{{choice.choice_text}} -- {{choice.votes}} vote{{choice.votes|pluralize}}&lt;/li&gt;
      {% endfor %}
  &lt;/ul&gt;
  
  &lt;a href="{% url 'polls:details' question.id }"&gt;Vote again&lt;/a&gt;
  {% endblock%}
  </code></pre>
  
  <p>This is urls.py file of polls app.</p>
  
  <h2><code>urls.py</code>:</h2>
  
  <pre><code>from django.conf.urls import url
  from . import views
  
  urlpatterns=[
      url(r"^$",views.index,name="index"),  #127.0.0.1:8000/polls
      url(r"^(?P&lt;question_id&gt;[0-9]+)/$",views.details,name="details"),
      url(r"^(?P&lt;question_id&gt;[0-9]+)/results$",views.results,name="result"),
      url(r"^(?P&lt;question_id&gt;[0-9]+)/vote$",views.vote,name="vote"),
  ]
  </code></pre>
  
  <h2><code>views.py</code>:</h2>
  
  <pre><code>from django.shortcuts import render,get_object_or_404
  from django.http import HttpResponse,HttpResponseRedirect
  # from django.core.urlresolvers import reverse
  from .models import Question
  from django.urls import reverse
  
  
  def results(request,question_id):
      question=get_object_or_404(Question,pk=question_id)
      return render(request,"polls/results.html",{"question":question})
  
  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:
          return render(request,"polls/details.html",{'question':question,"error_message":"Please select a choice"})
      else:
          selected_choice.votes+=1
          selected_choice.save()
  
          return HttpResponseRedirect(reverse("polls:results",args=(question.id,)))
  </code></pre>