Demonstration of private variables, one using name mangling of attributes prepended by a double underscore, and using a closure like in javascript

myclass.py

def myclass_factory():
    """
    Run this test with nosetests --with-doctest myclass.py

    >>> myclass = myclass_factory()
    >>> myclass.__private_attribute
    Traceback (most recent call last):
        ...
    AttributeError: 'MyClass' object has no attribute '__private_attribute'

    >>> myclass2 = myclass_factory()
    >>> myclass.push(1)
    >>> myclass2.push(2)
    >>> myclass.pop()
    1
    >>> myclass.pop()
    Traceback (most recent call last):
        ...
    IndexError: pop from empty list

    >>> myclass2.pop()
    2
    """

    # this variable is inaccessible, and unique for each call to myclass_factory
    private_variable = []

    class MyClass(object):
        def __init__(self):
            self.__private_attribute = 1

        def push(self, obj):
            private_variable.append(obj)

        def pop(self):
            return private_variable.pop()

    return MyClass()