[Tutor] How to access an instance variable of a superclass from an instance of the subclass?

[boB Stepp]

I am trying to wrap my head around the mechanics of inheritance in
Python 3.  I thought that all attributes of a superclass were
accessible to an instance of a subclass.  But when I try the
following:

py3: class A:
...     def __init__(self):
...             self.aa = 'class A'
...
py3: class B(A):
...     def __init__(self):
...             self.bb = 'class B'
...
py3: a = A()
py3: b = B()
py3: b.aa
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'B' object has no attribute 'aa'

I am unsuccessful.  The only way I have been able to access an
attribute aa of class A is to make aa a class variable.  Then I
succeed:

py3: class A:
...     aa = 'class A'
...
py3: class B(A):
...     def __init__(self):
...             self.b = 'class B'
...
py3: a = A()
py3: b = B()
py3: b.aa
'class A'

Obviously I am horribly misunderstanding something, and being
currently sleepy is not helping my cause.

Help, please?


-- 
boB