Beginner's Question (or bug in python?)

[Rolf Magnus]

Hello. I have a problem understanding why the behaviour of python depends 
on class names. I have the following python script:

#!/usr/bin/python

class Fred:

        def __init__(self):
                print('initializing fred')

        def __del__(self):
                print('deleting fred')

        def test(self):
                print('Hello world')


class Foo(Fred):

        def __init__(self):
                Fred.__init__(self)
                print ('initializing foo')

        def __del__(self):
                print('deleting foo');
                Fred.__del__(self)

x = Foo()
x.test()


If I execute this, I get the following:

initializing fred
initializing foo
Hello world
deleting foo
Exception exceptions.AttributeError: "'None' object has no attribute 
'__del__'" in <method Foo.__del__ of Foo instance at 80c3c00> ignored


If I instead call the base class Hans instead of Fred, it works as expected:

initializing fred
initializing foo
Hello world
deleting foo
deleting fred

This seems to be the case for Python 1.52 and 2.1 (not sure about 2.1, 
because I only tested the first case and got the error message).
And if I add a "del x" after the last line, it works in both cases. This 
seems odd to me, but since I am a python beginner, there is perhaps 
something important I don't know.