title: Django: check whether an object already exists before adding
body: <p>How do I check whether an object already exists, and only add it if it does <em>not</em> already exist?</p>
  <p>Here's the code - I don't want to add the follow_role twice in the database if it already exists. How do I check first? Use get() maybe - but then will Django complain if get() doesn't return anything?</p>
  <pre><code>current_user = request.user
  follow_role = UserToUserRole(from_user=current_user, to_user=user, role='follow')
  follow_role.save()
  </code></pre>