title: Python DataFrame: transpose one column into multiple column
body: <p>I have a dataframe like below:</p>
  
  <pre><code>df = pd.DataFrame({'month':['2017-09-27','2017-09-27','2017-09-28','2017-09-29'],'Cost':[100,500,200,300]})
  </code></pre>
  
  <p>How can I get a df like this: </p>
  
  <pre><code>2017-09-27   2017-09-28    2017-09-29
    100            200          300
    500            NULL         NULL  
  </code></pre>
  
  <p>Thanks in advance!</p>