title: Calculating Excel sheets without opening them (openpyxl or xlwt)
body: <p>I made a script that opens a .xls file, writes a few new values in it, then saves the file.</p>
  <p>Later, the script opens it again, and wants to find the answers in some cells which contain formulas.</p>
  <p>If I call that cell with openpyxl, I get the formula (ie: <code>&quot;=A1*B1&quot;</code>).
  And if I activate <code>data_only</code>, I get nothing.</p>
  <p>Is there a way to let Python calculate the .xls file? (or should I try PyXll?)</p>