title: How to change data types "object" in Pandas dataframe after importing a CSV?
body: <p>I have imported a CSV file as a Pandas dataframe. When I run <code>df.dtypes</code> I get most columns as "object", which is useless for taking into Bokeh for charts.</p>
  
  <ol>
  <li>I need to change a column as <code>int</code>, another column as <code>date</code>, and the rest as strings.</li>
  <li>I see the data types only once I import it.  Would you recommend changing it during import (how?), or after import?</li>
  </ol>