title: django - url pattern to match url safe base64 string
body: <p>I am using </p>
  
  <pre><code>import base64
  string_for_url = base64.urlsafe_b64encode(string_to_format)
  </code></pre>
  
  <p>but I'm not sure how to match the generated string in a url pattern.  I found this regex: <code>(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$</code> but I don't understand how to convert it into a named group.  As you can tell my regex knowledge is pretty limited.</p>
  
  <p>Thanks for any help in advance.</p>