title: TypeError: 'generator' object is not subscriptable
body: <pre><code>import openpyxl
  wb = openpyxl.load_workbook('example.xlsx')
  sheet = wb.active
  sheet.columns[1]
  Traceback (most recent call last):
    File "&lt;pyshell#3&gt;", line 1, in &lt;module&gt;
      sheet.columns[1]
  TypeError: 'generator' object is not subscriptable
  </code></pre>
  
  <p>I'm a beginner in Python and this is the first time for me to post my question.
  I'm stuck with the TypeError above saying, 'generator' object is not subscriptable. I think I exactly typed the code written on a website. 
  The URL of the website is <a href="https://automatetheboringstuff.com/chapter12/" rel="nofollow noreferrer">https://automatetheboringstuff.com/chapter12/</a></p>
  
  <p>Please help me to deal with this error.</p>