title: Find mixed types in Pandas columns
body: <p>Ever so often I get this warning when parsing data files:</p>
  
  <pre><code>WARNING:py.warnings:/usr/local/python3/miniconda/lib/python3.4/site-
  packages/pandas-0.16.0_12_gdcc7431-py3.4-linux-x86_64.egg/pandas
  /io/parsers.py:1164: DtypeWarning: Columns (0,2,14,20) have mixed types. 
  Specify dtype option on import or set low_memory=False.
            data = self._reader.read(nrows)
  </code></pre>
  
  <p>But if the data is large (I have 50k rows), how can I find WHERE in the data the change of dtype occurs?</p>