title: Django: formats of urlpatterns in urls.py
body: <p>I noticed that in Django there are two formats of <code>urlpatterns</code> in file <code>urls.py</code>:</p>
  
  <pre><code>urlpatterns = [
      url(...),
      url(...),
  ]
  </code></pre>
  
  <p>and </p>
  
  <pre><code>urlpatterns = pattern('',
      url(...),
      url(...),
  )
  </code></pre>
  
  <p>The first is a list of <code>url</code> instances, and the second invokes the <code>pattern</code> module with an empty string and a number of <code>url</code> instances as parameters.</p>
  
  <ol>
  <li>What is the difference between the two?</li>
  <li>What is the purpose of an empty string in the second format?</li>
  <li>Which one is recommended to use?</li>
  </ol>