title: How to select columns from dataframe by regex
body: <p>I have a dataframe in python pandas. The structure of the dataframe is as the following: </p>
  
  <pre><code>   a    b    c    d1   d2   d3 
     10   14   12   44  45    78
  </code></pre>
  
  <p>I would like to select the columns which begin with d. Is there a simple way to achieve this in python . </p>