title: Python openpyxl read until empty cell
body: <p>I'm trying to read one column out of my Excel-file until it hits an empty cell, then it needs to stop reading.
  My code so far:</p>
  
  <pre><code>import openpyxl
  import os
  
  def main():
      filepath = os.getcwd() + "\test.xlsx"
  
      wb = openpyxl.load_workbook(filename=filepath, read_only=True)
      ws = wb['Tab2']
  
      for i in range(2, 1000):
          cellValue = ws.cell(row=i, column=1).Value
          if cellValue != None:
              print(str(i) + " - " + str(cellValue))
          else:
              break;
  
  if __name__ == "__main__":
      main() 
  </code></pre>
  
  <p>By running this i get the following error when it hits an empty cell. Does anybody know how i can prevent this from happening.</p>
  
  <pre><code>Traceback (most recent call last):
    File "testFile.py" in &lt;module&gt;
        main()
        cellValue = sheet.cell(row=i, column=1).value
    File "C:\Python34\lib\openpyxl\worksheet\worksheet.py", line 353, in cell
        cell = self._get_cell(row, column)
    File "C:\Python34\lib\openpyxl\worksheet\read_only.py", line 171, in _get_cell
        cell = tuple(self.get_squared_range(column, row, column, row))[0]
  IndexError: tuple index out of range
  </code></pre>