'Convenience access by Excel style address'

def __getitem__(self, key):

    if isinstance(key, slice):
        return self.iter_rows('{0}:{1}'.format(key.start, key.stop))
    if (':' in key):
        return self.iter_rows(key)
    (row, column) = coordinate_to_tuple(key)
    return self._get_cell(row, column)
