title: Working with openpyxl. making a list out of a column
body: <p>I am working with a big excel file.
  I am using </p>
  
  <pre><code>wb = load_workbook(filename='my_file.xlsx')
  ws = wb['Sheet1']
  </code></pre>
  
  <p>I don't want to alter the worksheet in any way. I just want to take data from several columns and work with them.
  My understanding is that I can't just call a column and use <code>.tolist()</code> because all the values are stored in excel. </p>