title: Remove duplicate rows with certain column combination in excel using python
body: <p>I have a python program which reads excel documents. I need to allow only the first appearance of certain column combinations.
  Eg:</p>
  
  <pre><code>    A     |  B
    -------------
    1.  200 | 201   
    2.  200 | 202
    3.  200 | 201
    4.  200 | 203
    5.  201 | 201
    6.  201 | 202
    .............
  </code></pre>
  
  <p>I want remove/skip the third row where the duplication found and write it to a CSV file.
  Here is the function I've been trying so far. But it's not working.</p>
  
  <pre><code>def validateExcel(filename):
     xls=xlrd.open_workbook(filename)  
     setcount = 0
     column = 0
     count = 0
     # sheetcount = 0
     for sheet in xls.sheets():
         header=""
         # sheetcount = sheetcount + 1
         number_of_rows = sheet.nrows
         number_of_columns = sheet.ncols
         sheetname = sheet.name          
         mylist = []
         for row in range (1, number_of_rows):  
             mylist = []
             for col in range(0, 2):      
                 mylist.append(sheet.cell_value(row, col))
  
             print mylist
  
             myset = set(mylist)
  
             print myset
  </code></pre>