[疑问] _tuple 是哪里来的变量呢？？

ALL code:

>>> Point = namedtuple('Point', ['x', 'y'], verbose=True)
class Point(tuple):
'Point(x, y)'

__slots__ = ()

_fields = ('x', 'y')

def __new__(_cls, x, y):
'Create a 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 __repr__(self):
'Return a nicely formatted representation string'
return 'Point(x=%r, y=%r)' % self

def _asdict(self):
'Return a new OrderedDict which maps field names to their values'
return OrderedDict(zip(self._fields, self))

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' % kwds.keys())
return result

def __getnewargs__(self):
'Return self as a plain tuple. Used by copy and pickle.'
return tuple(self)

__dict__ = _property(_asdict)

def __getstate__(self):
'Exclude the OrderedDict from pickling'
pass

x = _property(_itemgetter(0), doc='Alias for field number 0')

y = _property(_itemgetter(1), doc='Alias for field number 1')

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连接：https://docs.python.org/2/library/collections.html?highlight=collection#namedtuple-factory-function-for-tuples-with-named-fields