title: ValueError: row index was 65536, not allowed by .xls format
body: <p>Currently, I am trying to edit an existing excel file using xlwt. I do not want to edit directly on the excel, so I first make a copy.</p>
  
  <pre><code>new_wb = xlutils.copy(file_location)
  </code></pre>
  
  <p>From this copy, I used the xlwt module to write a new column into the newly copied excel file and save. However, I get an error when I try to copy:</p>
  
  <pre><code>ValueError: row index was 65536, not allowed by .xls format
  </code></pre>
  
  <p>I am a little confused because the file I duplicate is a xlsx file, not xls. I never use the xls format in my code. </p>
  
  <p>Any guidance would be greatly appreciated. </p>