code: def getDataRowCount(self):
      
      numLines = self._getTotalLineCount()
  
      if numLines == 0:
        # this may be the case in a file opened for write before the
        # header rows are written out
        assert self._mode == self._FILE_WRITE_MODE and self._recordCount == 0
        numDataRows = 0
      else:
        numDataRows = numLines - self._NUM_HEADER_ROWS
  
      assert numDataRows >= 0
  
      return numDataRows
docs: :returns: (int) count of data rows in dataset (excluding header lines)