Python中的繼承和__dict__ 3

Question

我正在閱讀this blog post on OOP in python 3。在這裏面有：

class Door: 
    colour = 'brown' 

    def __init__(self, number, status): 
     self.number = number 
     self.status = status 

    @classmethod 
    def knock(cls): 
     print("Knock!") 

    def open(self): 
     self.status = 'open' 

    def close(self): 
     self.status = 'closed' 

class SecurityDoor: 
    locked = True 

    def __init__(self, number, status): 
     self.door = Door(number, status) 

    def open(self): 
     if self.locked: 
      return 
     self.door.open() 

    def __getattr__(self, attr): 
     return getattr(self.door, attr) 

當我這樣做：

>>> sdoor = SecurityDoor(1, 'closed') 
>>> sdoor.__dict__ 
{'door': <__main__.Door object at 0x0279A250>} 

爲什麼沒有 「鎖定：真」，在屬性字典？畢竟，「鎖定」是屬性

Answer 1

爲什麼在屬性字典中沒有「locked：True」？

因爲你正在檢查例如快譯通，但locked是一個類屬性。你可以使用self.__class__.__dict__找到它。

如果您需要看到的所有屬性，包括繼承和class屬性，使用insect.getmembers()或內置dir功能：

>>> import inspect 
>>> class A(object): 
...  b = 1 
...  def __init__(self): 
...   self.c = 1 
... 
>>> a = A() 

>>> inspect.getmembers(a) 
[('__class__', <class '__main__.A'>), ('__delattr__', <method-wrapper '__delattr__' of A object at 0x10d47f1d0>), ('__dict__', {'c': 1}), ('__doc__', None), ('__format__', <built-in method __format__ of A object at 0x10d47f1d0>), ('__getattribute__', <method-wrapper '__getattribute__' of A object at 0x10d47f1d0>), ('__hash__', <method-wrapper '__hash__' of A object at 0x10d47f1d0>), ('__init__', <bound method A.__init__ of <__main__.A object at 0x10d47f1d0>>), ('__module__', '__main__'), ('__new__', <built-in method __new__ of type object at 0x10d0d7280>), ('__reduce__', <built-in method __reduce__ of A object at 0x10d47f1d0>), ('__reduce_ex__', <built-in method __reduce_ex__ of A object at 0x10d47f1d0>), ('__repr__', <method-wrapper '__repr__' of A object at 0x10d47f1d0>), ('__setattr__', <method-wrapper '__setattr__' of A object at 0x10d47f1d0>), ('__sizeof__', <built-in method __sizeof__ of A object at 0x10d47f1d0>), ('__str__', <method-wrapper '__str__' of A object at 0x10d47f1d0>), ('__subclasshook__', <built-in method __subclasshook__ of type object at 0x7fc6b8638070>), ('__weakref__', None), ('b', 1), ('c', 1)] 

>>> dir(a) 
['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'b', 'c'] 

>>> a.__class__.__dict__ 
dict_proxy({'__module__': '__main__', 'b': 1, '__dict__': <attribute '__dict__' of 'A' objects>, '__weakref__': <attribute '__weakref__' of 'A' objects>, '__doc__': None, '__init__': <function __init__ at 0x10d4791b8>})