【3.7】数据封装和私有属性

　　• 在Python中，实例属性如果以双下划线开头，那么这个属性就是一个私有属性

class Test:
    def __init__(self, x):
        self.__x = x

    def the_print(self):
        print(self.__x)


t = Test(1)
print(t.__x)
t.the_print()

Traceback (most recent call last):
  File "demo.py", line 14, in <module>
    print(t.__x)
AttributeError: 'Test' object has no attribute '__x'

　　但是，Python实现这种私有属性的方法，仅仅是通过改变该变量的名称来达到的

class Test:
    def __init__(self, x):
        self.__x = x

    def the_print(self):
        print(self.__x)


t = Test(1)
print(t.__dir__())
print(t._Test__x)
t.the_print()

['_Test__x', '__module__', '__init__', 'the_print', '__dict__', '__weakref__', '__doc__', '__repr__', '__hash__', '__str__', '__getattribute__', '__setattr__', '__delattr__', '__lt__',
'__le__', '__eq__', '__ne__', '__gt__', '__ge__', '__new__', '__reduce_ex__', '__reduce__', '__subclasshook__', '__init_subclass__', '__format__', '__sizeof__', '__dir__', '__class__']
1
1

　　__x --> _Test__x