[Python-Dev] PEP 442: Safe object finalization

Sat May 18 15:56:38 CEST 2013

On 18/05/2013 9:59am, Antoine Pitrou wrote:
> This PEP proposes to turn CI disposal into the following sequence (new
> steps are in bold):
>> 1. Weakrefs to CI objects are cleared, and their callbacks called. At
> this point, the objects are still safe to use.
>> 2. **The finalizers of all CI objects are called.**

How do you know that one of the finalizers will not do something which 
causes another to fail?
Presumably the following would cause an AttributeError to be printed:
 class Node:
 def __init__(self):
 self.next = None
 def __del__(self):
 print(self, self.next)
 del self.next # break Node object
 a = Node()
 b = Node()
 a.next = b
 b.next = a
 del a, b
 gc.collect()
Are there are less contrived examples which will cause errors where 
currently there are none?
-- 
Richard