title: Pandas: replace empty cell to 0
body: <p>I have a data frame <code>results</code> that contains empty cells and I would like to replace all empty cells with 0. </p>
  
  <p>So far I have tried using pandas' <code>fillna</code>:</p>
  
  <pre><code>result.fillna(0)
  </code></pre>
  
  <p>and <code>replace</code>:</p>
  
  <pre><code>result.replace(r'\s+', np.nan, regex=True)
  </code></pre>
  
  <p>However, both with no success. </p>