title: openpyxl: ValueError: dtype: int64 to Excel
body: <p>I am combining two .csv file and writing a new .xlsx file.</p>
  
  <p>The code goes like this:</p>
  
  <pre><code>ODEMPTY = pandas.read_csv('OD_Empty_unduplicated.csv')
  ODNEW = pandas.read_csv('OD_Out.csv')
  
  ODNEW = ODNEW.append(ODEMPTY)
  
  wb = openpyxl.load_workbook('cm2011.xlsx')
  sheet = wb.get_sheet_by_name('Sheet1')
  
  for i in range(len(ODNEW)):
     sheet['A'+ str(i+1)].value = ODNEW['comm'][i] # start writing on A1 not A0
     sheet['B'+ str(i+1)].value = ODNEW['ONode'][i]
     sheet['C'+ str(i+1)].value = ODNEW['DNode'][i]
     sheet['D'+ str(i+1)].value = ODNEW['quantity'][i]
     sheet['E'+ str(i+1)].value = ODNEW['startRR'][i]
  </code></pre>
  
  <p>Error: ValueError: dtype: int64 to Excel</p>