title: Detecting Blank Excel Cell using python
body: <p>I have written a python code for converting data from multiple excel files to single csv file however it is not working. I tried XL_CELL_EMPTY or XL_CELL_BLANK in place of None in following program. But nothing is working. It is giving following error </p>
  
  <pre><code>Traceback (most recent call last):
    File "Excel_to_CSV_1.py", line 35, in &lt;module&gt;
      while Sh_B1.cell(i,j).value  != None : 
    File "/usr/lib/pymodules/python2.7/xlrd/sheet.py", line 245, in cell
      self._cell_types[rowx][colx],
  IndexError: array index out of range
  </code></pre>
  
  <p>This is the Program:</p>
  
  <pre><code>import xlrd
  import os.path
  from xlrd import open_workbook,empty_cell
  book1 = xlrd.open_workbook("Excel_1.xls")
  Sh_B1 = book1.sheet_by_index(0)
  book2 = xlrd.open_workbook("Excel_2.xls")
  Sh_B2 = book2.sheet_by_index(0)
  i = 1
  j = 1 
  file = open("Output.txt", "w")
  while Sh_B1.cell(i,j).value != None :
      while Sh_B1.cell(i,j).value  != None : 
          D1 = Sh_B1.cell(i,j).value
          D2 = Sh_B2.cell(i,j).value
          DB1 = str(D1)+ "," + str(D2)
          file.write("".join(DB1+ "\n"))
          j = j + 1
      j = 1
      print "j=1" 
      i = i + 1
  file.close
  </code></pre>
  
  <p>Where am I going wrong?</p>