This is what I'm trying to do in Python: 

```
class BaseClass:
    def __init__(self):
        print 'The base class constructor ran!'
        self.__test = 42

class ChildClass(BaseClass):

    def __init__(self):
        print 'The child class constructor ran!'
        BaseClass.__init__(self)

    def doSomething(self):
        print 'Test is: ', self.__test

test = ChildClass()
test.doSomething()

```

Which results in: 

```
AttributeError: ChildClass instance has no attribute '_ChildClass__test'

```

What gives? Why doesn't this work as I expect?