title: Will extend create a new copy in Python
body: <p>In the following code, why does <code>w</code> still hold the <code>5</code> after popping the <code>5</code> from <code>v</code>?</p>
  
  <pre><code>&gt;&gt;&gt; w = [1,2,3]
  &gt;&gt;&gt; v = [4,5]
  &gt;&gt;&gt; w.extend(v)
  &gt;&gt;&gt; w
  [1, 2, 3, 4, 5]
  &gt;&gt;&gt; v
  [4, 5]
  &gt;&gt;&gt; v.pop()
  5
  &gt;&gt;&gt; v
  [4]
  &gt;&gt;&gt; w
  [1, 2, 3, 4, 5]
  </code></pre>