python property疑惑,该怎么处理

python property疑惑
1：class filepro(object):
  def __init__(self,val):
  self._val=val
  ...
2：class filepro(object):
  def __init__(self,val):
  self.val=val
  ....
   
为什么第一个可以返回一个异域数值。
如果使用第二就返回AttributeError 异常呢？
在网上查了一下，说 _val是property私有成员，难道是指定property的？
为什么在其它OOP定义就没有这个问题呢？

 

[解决办法]
LZ说的是带双下划线的：

Python code

>>> class filepro(object):...     def __init__(self,val):...         self.__val=val...        >>> f = filepro(100)>>> f.__valTraceback (most recent call last):  File "<interactive input>", line 1, in <module>AttributeError: 'filepro' object has no attribute '__val'>>>
[解决办法]
严格来说，python class 没有完全的private，
就算是双下划的话，也可以写，


"mangling rules are designed mostly to avoid accidents; it still is possible to access or modify a variable that is considered private. This can even be useful in special circumstances, such as in the debugger."


mangling name here is  

__val in filepro  
become  
_filepro__val


>>> class filepro(object):
...     def __init__(self,val):
...         self.__val=val
...     def get_val(self):
...         return self.__val
...  
>>> f = filepro(100)
>>> f.get_val()
100
>>> f._filepro__val = 200
>>> f.get_val()
200
>>>