example2.py 文件源码

def named_tuple(classname, fieldnames):
    # Populate a dictionary of field property accessors
    cls_dict = { name: property(operator.itemgetter(n))
                 for n, name in enumerate(fieldnames) }

    # Make a __new__ function and add to the class dict
    def __new__(cls, *args):
        if len(args) != len(fieldnames):
            raise TypeError('Expected {} arguments'.format(len(fieldnames)))
        return tuple.__new__(cls, (args))

    cls_dict['__new__'] = __new__

    # Make the class
    cls = types.new_class(classname, (tuple,), {}, 
                           lambda ns: ns.update(cls_dict))
    cls.__module__ = sys._getframe(1).f_globals['__name__']
    return cls