当我运行这个(2.7.3)时,我得到这个输出:
'Slotted1' object has no attribute 'c'
attribute c added to <class '__main__.Slotted2'>
我不明白 Slotted1 和 Slotted2 之间的行为差异。谁能解释一下吗?
from ctypes import *
class BracedStructure(Structure):
def __init__(self, **args):
super(BracedStructure,self).__init__(**args)
class Slotted1(Structure):
__slots__ = ['a','b']
_fields_ = [('a',c_int8),('b',c_int8)]
def __init__(self, **args):
super(Slotted1,self).__init__(**args)
def attemptToAddField(self):
self.c = '?'
print 'attribute c added to %s' % self.__class__
class Slotted2(BracedStructure):
__slots__ = ['a','b']
_fields_ = [('a',c_int8),('b',c_int8)]
def __init__(self, **args):
super(Slotted2,self).__init__(**args)
def attemptToAddField(self):
self.c = '?'
print 'attribute c added to %s' % self.__class__
if '__main__' == __name__:
s1 = Slotted1(a=1,b=2)
try:
s1.attemptToAddField()
except AttributeError as e:
print e
s2 = Slotted2(a=1,b=2)
try:
s2.attemptToAddField()
except AttributeError as e:
print e
最佳答案
看看这个:http://docs.python.org/reference/datamodel.html#slots
When inheriting from a class without
__slots__
, the__dict__
attribute of that class will always be accessible, so a__slots__
definition in the subclass is meaningless.
碰巧 BracedStructure 没有 __slots__
,因此它覆盖了 Slotted2
中的 __slots__
声明。
关于python - __slots__、_fields_ 和继承的交叉点出现异常,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/11818711/