title: estimate the average value group by a specific column using python
body: <p>I have an ascii file containing 2 columns as following;</p>
  <pre><code>id value
  1  15.1
  1  12.1 
  1  13.5
  2  12.4
  2  12.5
  3  10.1
  3  10.2
  3  10.5
  4  15.1
  4  11.2
  4  11.5
  4  11.7
  5  12.5
  5  12.2
  </code></pre>
  <p>I want to estimate the average value of column &quot;value&quot; for each id (i.e. group by id)</p>
  <p>Is it possible to do that in python using numpy or pandas ?</p>