python - 在 __setattr__ 中访问对象的属性

Question

今天 Python 咬了我。我试图在其 __setattr__ 实现中访问对象的属性 - 我不知道如何访问。到目前为止，这是我尝试过的:

class Test1(object):
    def __init__(self):
        self.blub = 'hi1'

    def __setattr__(self, name, value):
        print self.blub

class Test2(object):
    def __init__(self):
        self.blub = 'hi2'

    def __setattr__(self, name, value):
        print object.__getattr__(self, 'blub')

class Test3(object):
    def __init__(self):
        self.blub = 'hi3'

    def __setattr__(self, name, value):
        print object.__getattribute__(self, 'blub')

class Test4(object):
    def __init__(self):
        self.blub = 'hi4'

    def __setattr__(self, name, value):
        print self.__getattr__('blub')

class Test5(object):
    def __init__(self):
        self.blub = 'hi5'

    def __setattr__(self, name, value):
        print self.__getattribute__('blub')

class Test6(object):
    def __init__(self):
        self.blub = 'hi6'

    def __setattr__(self, name, value):
        print self.__dict__['blub']

测试:

try:
    TestX().bip = 'bap'
except Exception as ex:
    print ex

X 从 1 到 6

输出:

'Test1' object has no attribute 'blub'
type object 'object' has no attribute '__getattr__'
'Test3' object has no attribute 'blub'
'Test4' object has no attribute '__getattr__'
'Test5' object has no attribute 'blub'
'blub'

有什么建议吗？

Answer 1

因为在 __init__ 中，它试图设置调用 __setattr__ 的 blub；它没有设置任何内容，只是尝试访问(和打印)blub，但没有找到任何内容并引发错误。检查这个:

>>> class Test2(object):
  def __init__(self):
    print "__init__ called"
    self.blub = 'hi2'
    print "blub was set"

  def __setattr__(self, name, value):
    print "__setattr__ called"
    print self.blub


>>> Test2()
__init__ called
__setattr__ called

Traceback (most recent call last):
  File "<pyshell#10>", line 1, in <module>
    Test2()
  File "<pyshell#9>", line 4, in __init__
    self.blub = 'hi2'
  File "<pyshell#9>", line 9, in __setattr__
    print self.blub
AttributeError: 'Test2' object has no attribute 'blub'
>>>