title: pandas get_level_values for multiple columns
body: <p>Is there a way to get the result of <a href="http://pandas.pydata.org/pandas-docs/version/0.17.0/generated/pandas.Index.get_level_values.html" rel="noreferrer"><code>get_level_values</code></a> for more than one column?</p>
  
  <p>Given the following <code>DataFrame</code>:</p>
  
  <pre><code>         d
  a b c     
  1 4 10  16
      11  17
    5 12  18
  2 5 13  19
    6 14  20
  3 7 15  21
  </code></pre>
  
  <p>I wish to get the values (<em>i.e.</em> list of tuples) of levels <code>a</code> and <code>c</code>:</p>
  
  <pre><code>[(1, 10), (1, 11), (1, 12), (2, 13), (2, 14), (3, 15)]
  </code></pre>
  
  <p><strong>Notes:</strong></p>
  
  <ul>
  <li><p>It is impossible to give <code>get_level_values</code> more than one level (<em>e.g.</em> <code>df.index.get_level_values(['a','c']</code>)</p></li>
  <li><p>There's a workaround in which one could use <code>get_level_values</code> over each desired column and <code>zip</code> them together:</p></li>
  </ul>
  
  <p>For example:</p>
  
  <pre><code>a_list = df.index.get_level_values('a').values
  c_list = df.index.get_level_values('c').values
  
  print([i for i in zip(a_list,c_list)])
  [(1, 10), (1, 11), (1, 12), (2, 13), (2, 14), (3, 15)]
  </code></pre>
  
  <p>but it get cumbersome as the number of columns grow.</p>
  
  <ul>
  <li>The code to build the example <code>DataFrame</code>:</li>
  </ul>
  
  <p><code>df = pd.DataFrame({'a':[1,1,1,2,2,3],'b':[4,4,5,5,6,7,],'c':[10,11,12,13,14,15], 'd':[16,17,18,19,20,21]}).set_index(['a','b','c'])</code></p>