title: XlsxWriter: set_column() with one format for multiple non-continuous columns
body: <p>I want to write my Pandas dataframe to Excel and apply a format to multiple individual columns (e.g., A and C but not B) using a one-liner as such:</p>
  
  <pre><code>writer = pd.ExcelWriter(filepath, engine='xlsxwriter')
  my_format = writer.book.add_format({'num_format': '#'})
  
  writer.sheets['Sheet1'].set_column('A:A,C:C', 15, my_format)
  </code></pre>
  
  <p>This results in the following error:</p>
  
  <blockquote>
    <p>File ".../python2.7/site-packages/xlsxwriter/worksheet.py", line 114, in column_wrapper</p>
    
    <p>cell_1, cell_2 = [col + '1' for col in args[0].split(':')]
    ValueError: too many values to unpack</p>
  </blockquote>
  
  <p>It doesn't accept the syntax <code>'A:A,C:C'</code>. Is it even possible to apply the same formatting without calling <code>set_column()</code> for each column?</p>