def __call__(self, *columns):
        "Returns an iterator over the specified columns."
        indexs = tuple(self.__columns[name][1] for name in columns)
        yield columns
        for row in sorted(self.__data_area):
            yield tuple(self.__data_area[row][index] for index in indexs)
Returns an iterator over the specified columns.
recipes/Python/577825_Rudimentary_Database_Engine/recipe-577825.py