title: Python pandas dataframe: filter columns using a list?
body: <p>I have a dataframe that is large: 100000 rows * 10000 cols</p>
  
  <p>Now I'm given a list of labels (call this list1) that do not match exactly with the labels of the columns in this dataframe, but match part of these labels. For example, a label in the dataframe might be "string1,D111" and the labels in list1 might look like "D111".</p>
  
  <p>So now basically I want to find out all these corresponding columns using list1, and then sum all these columns, what is the most efficient way to do this?</p>
  
  <pre><code>Dataframe:
         string1,D111       string2,D222          string3,D333   ......    stringn,Dnnn
  1         ..                   ..                     ..                     ..
  2
  3
  4
  5
  6
  ...
  
  
  My list1:  D111, D333,...Dxxx
  </code></pre>