实际上，很容易找出给定namedtuple的实现方式：如果verbose=True在创建给定参数时传递了关键字参数，则会打印其类定义：
>>> Point = namedtuple('Point', "x y", verbose=True)
from builtins import property as _property, tuple as _tuple
from operator import itemgetter as _itemgetter
from collections import OrderedDict
class Point(tuple):
'Point(x, y)'
__slots__ = ()
_fields = ('x', 'y')
def __new__(_cls, x, y):
'Create new instance of Point(x, y)'
return _tuple.__new__(_cls, (x, y))
@classmethod
def _make(cls, iterable, new=tuple.__new__, len=len):
'Make a new Point object from a sequence or iterable'
result = new(cls, iterable)
if len(result) != 2:
raise TypeError('Expected 2 arguments, got %d' % len(result))
return result
def _replace(_self, **kwds):
'Return a new Point object replacing specified fields with new values'
result = _self._make(map(kwds.pop, ('x', 'y'), _self))
if kwds:
raise ValueError('Got unexpected field names: %r' % list(kwds))
return result
def __repr__(self):
'Return a nicely formatted representation string'
return self.__class__.__name__ + '(x=%r, y=%r)' % self
@property
def __dict__(self):
'A new OrderedDict mapping field names to their values'
return OrderedDict(zip(self._fields, self))
def _asdict(self):
'''Return a new OrderedDict which maps field names to their values.
This method is obsolete. Use vars(nt) or nt.__dict__ instead.
'''
return self.__dict__
def __getnewargs__(self):
'Return self as a plain tuple. Used by copy and pickle.'
return tuple(self)
def __getstate__(self):
'Exclude the OrderedDict from pickling'
return None
x = _property(_itemgetter(0), doc='Alias for field number 0')
y = _property(_itemgetter(1), doc='Alias for field number 1')
因此，它是的子类，tuple具有一些额外的方法来赋予其必需的行为，_fields包含字段名称的类级常量以及property用于访问元组成员的属性的方法。
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