title: Python : In DataFrame, How to replace float value to string value?
body: <p>In my situation, I want </p>
  
  <p>input:  </p>
  
  <pre><code>No col1 col2 col3  
  1  -999 -999 -999  
  2    1    2    3  
  3    2    4  -999  
  4    3    5  blank  
  </code></pre>
  
  <p>output:  </p>
  
  <pre><code>No col1 col2 col3    
  1    .    .    .    
  2    1    2    3    
  3    2    4    .   
  4    3    5    .  
  </code></pre>
  
  <p>how to convert -999 --> '.' ?</p>