code: def xlsx_to_csv(self, infile, worksheet=0, delimiter=","):
          
          wb = load_workbook(self.getInputFile())
          sheet = wb.worksheets[worksheet]
          buffer = StringIO()
  
          # extract all rows
          for n, row in enumerate(sheet.rows):
              line = []
              for cell in row:
                  value = cell.value
                  if type(value) in types.StringTypes:
                      value = value.encode("utf8")
                  if value is None:
                      value = ""
                  line.append(str(value))
              print >>buffer, delimiter.join(line)
          buffer.seek(0)
          return buffer
docs: Convert xlsx to easier format first, since we want to use the
          convenience of the CSV library