Python中单下划线和双下划线

 
 class MyClass():
     def __init__(self):
             self.__superprivate = ""Hello""
             self._semiprivate = "", world!""

 mc = MyClass()
 print mc.__superprivate
Traceback (most recent call last):
  File """", line 1, in 
AttributeError: myClass instance has no attribute '__superprivate'
>>> print mc._semiprivate
, world!
>>> print mc.__dict__
{'_MyClass__superprivate': 'Hello', '_semiprivate': ', world!'}