title: Pandas: how to fill null values matching the right types of that column?
body: <p>The <a href="http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.fillna.html" rel="nofollow">Dataframe.fillna method</a> can fill null values with a default value. </p>
  
  <p>But when we have both string and numeric type columns, how to fill the numeric-type null cells with number 0, and fill the string-type null cells with string "0" or "blank"?</p>
  
  <p>EDIT:</p>
  
  <p>The table contains thousands of mixed-type columns, so it is not feasible to fillna for each column manually.</p>