>>> class MyClass():

...     def __init__(self):

...             self.__superprivate = "Hello"

...             self._semiprivate = ", world!"

...

>>> mc = MyClass()

>>> print mc.__superprivate

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

AttributeError: myClass instance has no attribute '__superprivate'

>>> print mc._semiprivate

, world!

>>> print mc.__dict__

{'_MyClass__superprivate': 'Hello', '_semiprivate': ', world!'}