title: Python Pandas Multi-index: Rename Specific Index Row Value
body: <p>My ultimate goal is to compute the <code>pct_change</code> for two rows within a (2, 2) multi-index dataframe but I want the <code>pct_change</code> row to appear below the other two rows.  I know about <code>pct_change()</code> method but that doesn't make a new row so instead I'm computing the pct_change as a separate dataframe and appending the <code>pct_change</code> row to an existing dataframe.  Here's an example dataframe.</p>
  
  <pre><code>df = pd.DataFrame(data={
    'A': [94128, 28198, -70.04], 'B': [3627, 1483, -59.11]},
                    index=pd.MultiIndex.from_tuples([('Label', '(Jun 1, 2014-Mar 31, 2015)'),
                                                     ('Label', '(Jun 1, 2015-Mar 31, 2016)'),
                                                     ('Label', '(Jun 1, 2015-Mar 31, 2016)')],
                                                    names=['Text', 'Period']))
  </code></pre>
  
  <p>Looks like this:</p>
  
  <pre><code>                                         A        B
  Text  Period                                       
  Label (Jun 1, 2014-Mar 31, 2015)  94128.00  3627.00
        (Jun 1, 2015-Mar 31, 2016)  28198.00  1483.00
        (Jun 1, 2015-Mar 31, 2016)    -70.04   -59.11
  </code></pre>
  
  <p>This is a multi-index and I want to rename the last <code>Period</code> row value to say <code>% Change</code>.</p>
  
  <p>Desired Output:</p>
  
  <pre><code>                                         A        B
  Text  Period                                       
  Label (Jun 1, 2014-Mar 31, 2015)  94128.00  3627.00
        (Jun 1, 2015-Mar 31, 2016)  28198.00  1483.00
                          % Change    -70.04   -59.11
  </code></pre>
  
  <p>Is what I'm trying to do even possible given its multi-index complexity?</p>
  
  <pre><code>&gt;&gt;&gt; df.index
  MultiIndex(levels=[['Label'], ['(Jun 1, 2014-Mar 31, 2015)', '(Jun 1, 2015-Mar 31, 2016)']],
             labels=[[0, 0, 0], [0, 1, 1]],
             names=['Text', 'Period'])
  </code></pre>