Python属性报错对象没有属性

Question

当我应用两个下划线时，出现错误 AttributeError: 'Organization' object has no attribute '__employees'这是代码。

 class Organization(object):
        __employees=[]

    google=Organization()
    google.__employees.append('Erik')

Python 没有实现私有(private)变量的概念。如果是这样，我会得到什么错误。如果我删除一个下划线代码，则执行时不会出错。

Answer 1

好吧，您已将其声明为私有(private)变量。

>>> class Organization(object):
...     __employees = []
... 
>>> google = Organization()
>>> google._Organization__employees.append('Erik')
>>> google._Organization__employees
['Erik']

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

如您所见，它使用 _Classname__Variablename 保存您的可变名称。在您的情况下，它是 _Organization__employees。

来自Python doc小号:

Any identifier of the form __spam (at least two leading underscores, at most one trailing underscore) is textually replaced with _classname__spam, where classname is the current class name with leading underscore(s) stripped. This mangling is done without regard to the syntactic position of the identifier, so it can be used to define class-private instance and class variables, methods, variables stored in globals, and even variables stored in instances. private to this class on instances of other classes.