title: How I can calculate standard deviation for rows of a dataframe?
body: <pre><code>df:  
  
  name   group   S1   S2  S3        
  A      mn      1    2   8         
  B      mn      4    3   5        
  C      kl      5    8   2        
  D      kl      6    5   5         
  E      fh      7    1   3         
  
  output: 
  
  std (S1,S2,S3)
  3.78
  1
  3
  0.57
  3.05
  </code></pre>
  
  <p>This is working for getting std for a column:</p>
  
  <pre><code>numpy.std(df['A'])
  </code></pre>
  
  <p>I want to do the same for rows</p>