circular references?

[Roy Smith]

To follow up on my own question, I've changed my main loop to look 
something like:

        [code to set func to the right subclass]
        page = apply (func, (self,))
        page.show()
        page.cleanup()

The page.cleanup() call is the new part, and the last thing to get 
executed before page drops out of scope (i.e. the enclosing function 
returns).  Cleanup just breaks the circular references:

class new_domain (netdbpage):
    def cleanup (self):
        self.record_set = None
        netdbpage.cleanup (self)

This makes everything work fine.  However, I'm still mystified as to the 
behavior I was observing.  I can understand the memory leak problem, but 
not the i/o problem.  I sure would like to know what was going on for 
real, but I'll admit that not understanding why my code works sure beats 
not understanding why it doesn't :-)

BTW, is there any functional difference between "self.record_set = None" 
and "del self.record_set", if the object in question is about to go out 
of scope anyway?  FAQ 4.17 says, "Normally, deleting (better: assigning 
None to) sys.exc_traceback will take care of this".  Why, in that 
situation, the preference of one over the other?