namedtuple

‍

手动实现namedtuple

import operator
import types
import sys

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))

    # Set the module to that of the caller
    cls.__module__ = sys._getframe(1).f_globals['__name__']
    return cls

"""
>>> Point = named_tuple('Point', ['x', 'y'])
>>> Point
<class '__main__.Point'>
>>> p = Point(4, 5)
>>> len(p)
2
>>> p.x
4
>>> p.y
5
>>> p.x = 2
Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
AttributeError: can't set attribute
>>> print('%s %s' % p)
4 5
>>>
"""

‍