def update(self, **assignments):
        "Changes all present rows with given assignments."
        assign = []
        for name, value in assignments.items():
            data_type, index = self.__columns[name]
            assert isinstance(value, data_type), \
            'Wrong datatype: {} ({!r}, {!r})'.format(name, value, data_type)
            assign.append((index, value))
        for row in self.__data_area.values():
            for index, value in assign:
                row[index] = value
Changes all present rows with given assignments.
recipes/Python/577825_Rudimentary_Database_Engine/recipe-577825.py