[Python-bugs-list] [ python-Feature Requests-515073 ] subtypable weak references

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Sat, 16 Feb 2002 16:06:05 -0800


Feature Requests item #515073, was opened at 2002-02-08 16:50
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Category: Type/class unification
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: David Abrahams (david_abrahams)
Assigned to: Nobody/Anonymous (nobody)
Summary: subtypable weak references

Initial Comment:
I want to be able to create a subtype of weakref.

Motivation: I use a trick to non-intrusively keep one 
Python object (ward) alive as long as another one 
(custodian) is: I build a weak reference to the 
custodian whose kill function object holds a reference 
to the ward. I "leak" the weakref, but the function 
decrements its refcount so it will eventually die. 
This scheme costs an extra allocation for the function 
object, and because there is a function object at all, 
there's no opportunity to re-use the weakref (please 
document this part of the re-use behavior, BTW!)

I also want the re-use algorithm to check for object 
and type equality so that I can avoid creating 
multiple such references.

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>Comment By: Martin v. Löwis (loewis)
Date: 2002-02-16 16:06

Message:
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user_id=21627

This is what the WeakKeyDictionary is for: use the custodian
as the key, and the ward as the value.

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