title: How to drop extra copy of duplicate index of Pandas Series?
body: <p>I have a Series <code>s</code> with duplicate index :</p>
  
  <pre><code>&gt;&gt;&gt; s
  STK_ID  RPT_Date
  600809  20061231    demo_str
          20070331    demo_str
          20070630    demo_str
          20070930    demo_str
          20071231    demo_str
          20060331    demo_str
          20060630    demo_str
          20060930    demo_str
          20061231    demo_str
          20070331    demo_str
          20070630    demo_str
  Name: STK_Name, Length: 11
  </code></pre>
  
  <p>And I just want to keep the unique rows and only one copy of the duplicate rows by:</p>
  
  <pre><code>s[s.index.unique()]
  </code></pre>
  
  <p><code>Pandas 0.10.1.dev-f7f7e13</code>  give the below error msg</p>
  
  <pre><code>&gt;&gt;&gt; s[s.index.unique()]
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
    File "d:\Python27\lib\site-packages\pandas\core\series.py", line 515, in __getitem__
      return self._get_with(key)
    File "d:\Python27\lib\site-packages\pandas\core\series.py", line 558, in _get_with
      return self.reindex(key)
    File "d:\Python27\lib\site-packages\pandas\core\series.py", line 2361, in reindex
      level=level, limit=limit)
    File "d:\Python27\lib\site-packages\pandas\core\index.py", line 2063, in reindex
      limit=limit)
    File "d:\Python27\lib\site-packages\pandas\core\index.py", line 2021, in get_indexer
      raise Exception('Reindexing only valid with uniquely valued Index '
  Exception: Reindexing only valid with uniquely valued Index objects
  &gt;&gt;&gt; 
  </code></pre>
  
  <p>So how to drop extra duplicate rows of series, keep the unique rows and only one copy of the duplicate rows in an efficient way ? (better in one line)</p>