Class Inheritance - What am I doing wrong?

[Arnaud Delobelle]

Brian Munroe <brian.e.munroe at gmail.com> writes:

> My example:
>
> class A(object):
>
> 	def __init__(self, name):
> 		self.__name = name
>
> 	def getName(self):
> 		return self.__name
>
> class B(A):
>
> 	def __init__(self,name=None):
> 		super(A,self).__init__()
>
> 	def setName(self, name):
> 		self.__name = name
>
> if __name__ == '__main__':
>
> 	a = A('class a')
> 	print a.getName()
>
> 	b = B('class b')
> 	print b.getName()
>
> 	b.setName('class b, reset')
> 	print b.getName()
>
> I get the following error:
>
> mtinky:~ brian$ python teste.py
> class a
> Traceback (most recent call last):
>   File "teste.py", line 23, in <module>
>     print b.getName()
>   File "teste.py", line 7, in getName
>     return self.__name
> AttributeError: 'B' object has no attribute '_A__name'
>
> Am I *not* using super() correctly?  Also, did I define my the class B
> constructor correctly?

You have fallen victim to the Name Mangling Trap [1].  Replace the
leading double underscore in the __name attribute with a single one,
and Python shall calm down and let your code behave as you expect it
to.

That is, if you also pass the name parameter to super(A,self).__init__
in B's __init__ method

[1] http://docs.python.org/ref/atom-identifiers.html

-- 
Arnaud