title: Drop the first (or any nth) column whose name contains a specific string from pandas DataFrame
body: <p>Let's say I have a pandas DataFrame as follows:</p>
  <pre><code>df = pd.DataFrame([[1,2,3,4,5],[6,7,8,9,10]],columns=['a1693','b1124','b113','a2609', 'a1'])
  </code></pre>
  <p>I want to drop, for example, <code>b1124</code>. How do I do it?</p>
  <p>I can get the column as a pd.Series by using the following code.</p>
  <pre><code>df.loc[:,df.columns.str.contains('b')].iloc[:,0]
  </code></pre>
  <p>But I don't know how to drop it from <code>df</code>.</p>
  <p>Also, if I want to do the same for multiple columns, i.e. drop <code>a1693</code> and <code>b1124</code>, how do I do that as well?</p>