title: Python slice with del statement
body: <p>Why does this:</p>
  
  <pre><code>del a[:]
  </code></pre>
  
  <p>delete all entries in the list <code>a</code>?</p>
  
  <p>As far as I understand, <code>a[:]</code> returns a copy of <code>a</code>. So shouldn't <code>del a[:]</code> delete the copy of <code>a</code>?</p>