views.py
class ContactView(generic.FormView):
    """Contact page & form."""
    form_class = ContactForm
    template_name = 'blog/contact.html'
    success_url = reverse_lazy('blog:success')

    def form_valid(self, form):
        form.send_email()
        return super(ContactView, self).form_valid(form)

def post_detail(request, year, month, day, post):
    post = get_object_or_404(Post, slug=post,
                                   status='published',
                                   publish__year=year,
                                   publish__month=month,
                                   publish__day=day)

    # List of active comments for this post
    comments = post.comments.filter(active=True)
    if request.method == 'POST':
        # A comment was posted
        comment_form = CommentForm(data=request.POST)

        if comment_form.is_valid():
            # Create Comment object but don't save to database yet
            new_comment = comment_form.save(commit=False)
            # Assign the current post to the comment
            new_comment.post = post
            # Save the comment to the database
            new_comment.save()
    else:
        comment_form = CommentForm()

    # List of similar posts
    post_tags_ids = post.tags.values_list('id', flat=True)
    similar_posts = Post.published.filter(tags__in=post_tags_ids).exclude(id=post.id)
    similar_posts = similar_posts.annotate(same_tags=Count('tags')).order_by('-same_tags',
                                                                             '-publish')[:4]
    return render(request, 'blog/post/detail.html', {'post': post,
                                                     'comments': comments,
                                                     'comment_form': comment_form,
                                                     'similar_posts': similar_posts})