>>> class Foo(object):
...     def __foo(self):
...         self.__bar()
...         __bar()
...         return self.__baz
... 
>>> from dis import dis
>>> dir(Foo)
['_Foo__foo', '__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__']
>>> dis(Foo._Foo__foo)
  3           0 LOAD_FAST                0 (self)
              3 LOAD_ATTR                0 (_Foo__bar)
              6 CALL_FUNCTION            0
              9 POP_TOP             

  4          10 LOAD_GLOBAL              0 (_Foo__bar)
             13 CALL_FUNCTION            0
             16 POP_TOP             

  5          17 LOAD_FAST                0 (self)
             20 LOAD_ATTR                1 (_Foo__baz)
             23 RETURN_VALUE