title: Removing single and range of columns in pandas
body: <p>What is the fastest way to drop <code>columns[3]</code> and <code>columns[9:15]</code>? 
  (I'm only able to remove the columns in 2 steps using the <code>df.drop</code> method)</p>
  
  <pre><code>    1  2  3  4  5  6 ..  n
  A   x  x  x  x  x  x ..  x
  B   x  x  x  x  x  x ..  x
  C   x  x  x  x  x  x ..  x 
  </code></pre>