title: how to handle xlsx file reading error ("assert tvalue is not None") using xlrd package?
body: <p>Below Python code is to read xls &amp; xlsx file. Im facing a problem while reading an xlsx file. Error is "assert tvalue is not None"</p>
  
  <pre><code>--&gt; workbook=xlrd.open_workbook("/home/perlzuser/sprint12/template.xlsx")
  sheet=workbook.sheet_by_index(0)    
  data=[[sheet.cell_value(r,c) for c in range(sheet.ncols)]for r in range (sheet.nrows)]
  print " ::",data
  </code></pre>
  
  <p>My error:::</p>
  
  <blockquote>
    <p>/home/perlzuser/Enthought/Canopy_32bit/User/lib/python2.7/site-packages/xlrd/xlsx.pyc
    in do_row(self, row_elem)
        723                     else:
        724                         bad_child_tag(child_tag)
    --> 725                 assert tvalue is not None
        726                 self.sheet.put_cell(rowx, colx, XL_CELL_TEXT, tvalue, xf_index)
        727             else:</p>
    
    <p>AssertionError:</p>
  </blockquote>
  
  <p>How to resolve this issue in python?</p>