title: using the .at[ ] and .iat[ ] accessors in pandas
body: <p>whenever I iterate though a pandas series on jupyter notebook console to modify values using set_value I get this FutureWarning: set_value is deprecated and will be removed in a future release. Please use .at[] or .iat[] accessors instead. </p>
  
  <p>How do I use .at[] or .iat[] in loops? </p>
  
  <pre><code>s = pd.Series([100 , 120.0 , 101.0 , 3.0 ])
  for l , v in s.iteritems():
      s.set_value(l, v + 4)
  </code></pre>