Python 2.7中的namedtuple
实现实现了__dict__
。我很困惑这是做什么的;如果已经定义了属性,为什么我们需要创建一个特殊的__dict__
?
C:\tmp> python
Python 2.7.12 |Anaconda 4.1.1 (64-bit)| (default, Jun 29 2016, 11:07:13) [MSC v.1500 64 bit (AMD64)] on win32
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>>> import collections
>>> x = collections.namedtuple('foo','bar baz', verbose=True)
class foo(tuple):
'foo(bar, baz)'
__slots__ = ()
_fields = ('bar', 'baz')
def __new__(_cls, bar, baz):
'Create new instance of foo(bar, baz)'
return _tuple.__new__(_cls, (bar, baz))
@classmethod
def _make(cls, iterable, new=tuple.__new__, len=len):
'Make a new foo 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 'foo(bar=%r, baz=%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 foo object replacing specified fields with new values'
result = _self._make(map(kwds.pop, ('bar', 'baz'), _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
bar = _property(_itemgetter(0), doc='Alias for field number 0')
baz = _property(_itemgetter(1), doc='Alias for field number 1')
答案 0 :(得分:3)
他们只是觉得这很方便。事实证明它是more hassle than it was worth,导致了酸洗和子类的问题,无论如何它在概念上令人困惑。更新的Python版本不再拥有它。