title: Facing problem with XLWT and XLRD - Reading and writing simultaneously
body: <p>I am facing a problem with xlrd and xlwt. Pasting the sample code
  below.</p>
  
  <pre><code>from xlwt import Workbook, Formula, XFStyle
  import xlrd
  
  book = Workbook()
  sheet1 = book.add_sheet('Sheet 1')
  myFontStyle = XFStyle()
  myFontStyle.num_format_str = '0.00'
  sheet1.write(0,0,10, myFontStyle)
  sheet1.write(0,1,20, myFontStyle)
  sheet1.write(1,0,Formula('AVERAGE(A1:B1)'), myFontStyle)
  book.save('formula.xls')
  
  wb = xlrd.open_workbook('formula.xls')
  sh = wb.sheet_by_index(0)
  for rownum in range(sh.nrows):
      print sh.row_values(rownum)
  </code></pre>
  
  <p>The idea is to write some values to Excel file, have some excel
  specific functions like LogNormal, StdDev etc and read the calculated
  values using XLRD.</p>
  
  <p>By running the above code, I get the following results which are
  undesirable:-</p>
  
  <pre><code>[10.0, 20.0]
  [u'', '']
  </code></pre>
  
  <p>Ideally I should have got 15 on the second row. It writes the Excel
  perfectly when I open it but XLRD does not return the results. I am
  stuck with this for a very critical project. Request you to kindly
  respond earliest.</p>
  
  <p>Thanks and Regards
  Tarun Pasrija </p>