Example of 'private' function in Python. _ = don't expose, __ = hide. http://stackoverflow.com/a/70900/1060378

gistfile1.py

class Foo(object):
  def __init__(self):
    self.__baz = 42
  def foo(self):
    print self.__baz
    
class Bar(Foo):
  def __init__(self):
    super(Bar, self).__init__()
    self.__baz = 21
  def bar(self):
    print self.__baz

>>> x = Bar()
>>> x.foo()
42
>>> x.bar()
21
>>> print x.__dict__
{'_Bar__baz': 21, '_Foo__baz': 42}