django sessions for beginners

1def index(request):
2    ...
3
4    num_authors = Author.objects.count()  # The 'all()' is implied by default.
5    
6    # Number of visits to this view, as counted in the session variable.
7    num_visits = request.session.get('num_visits', 0)
8    request.session['num_visits'] = num_visits + 1
9
10    context = {
11        'num_books': num_books,
12        'num_instances': num_instances,
13        'num_instances_available': num_instances_available,
14        'num_authors': num_authors,
15        'num_visits': num_visits,
16    }
17    
18    # Render the HTML template index.html with the data in the context variable.
19    return render(request, 'index.html', context=context)