title: How to do a transpose a dataframe group by key on pandas?
body: <p>I have this table from my database and I need a transpose group by survey_id</p>
  
  <pre><code>id  answer  survey_id   question_number questionid 
  216     0.0         69               3         2.0   
  217     3.0         69               4         3.0   
  218     0.0         69               5         4.0   
  219     0.0         69               6         5.0   
  221     0.0         69               8         7.0 
  </code></pre>
  
  <p>Like this:</p>
  
  <pre><code>Survey P01  P02 P03 P04 P05
  69     1    1   2   2   1
  </code></pre>
  
  <p>The cell is the answer and the column is format "P{question_number}"</p>
  
  <p>I'm using pandas 0.18.1.</p>
  
  <p>How can I do that?</p>