[Python-checkins] CVS: python/nondist/peps pep-0205.txt,1.9,1.10

[Fred L. Drake]

Update of /cvsroot/python/python/nondist/peps
In directory usw-pr-cvs1:/tmp/cvs-serv20323

Modified Files:
	pep-0205.txt 
Log Message:

Some minor updates to reflect the removal of .clear().  Added information
(preliminary) about proxy objects.


Index: pep-0205.txt
===================================================================
RCS file: /cvsroot/python/python/nondist/peps/pep-0205.txt,v
retrieving revision 1.9
retrieving revision 1.10
diff -C2 -r1.9 -r1.10
*** pep-0205.txt	2001/01/22 20:24:56	1.9
--- pep-0205.txt	2001/01/22 22:11:03	1.10
***************
*** 75,83 ****
      files, etc.).
  
!     A new module, weakref, will contain two new functions used to
!     create weak references.  weakref.new() will create a "weak
!     reference object" and optionally attach a callback which will be
!     called when the object is about to be finalized.
!     weakref.mapping() will create a "weak dictionary".
  
      A weak reference object will allow access to the referenced object
--- 75,85 ----
      files, etc.).
  
!     A new module, weakref, will contain new functions used to create
!     weak references.  weakref.new() will create a "weak reference
!     object" and optionally attach a callback which will be called when
!     the object is about to be finalized.  weakref.mapping() will
!     create a "weak dictionary".  A third function, weakref.proxy(),
!     will create a proxy object that behaves somewhat like the original
!     object.
  
      A weak reference object will allow access to the referenced object
***************
*** 100,110 ****
      dictionaries, weak dictionaries are not hashable.
  
!     The callbacks registered with weak reference objects or in weak
!     dictionaries must accept a single parameter, which will be the
!     weak-ly referenced object itself.  The object can be resurrected
!     by creating some other reference to the object in the callback, in
!     which case the weak reference generating the callback will still
!     be cleared but no weak references remaining to the object will be
!     cleared.
  
  
--- 102,124 ----
      dictionaries, weak dictionaries are not hashable.
  
!     Proxy objects are weak references that attempt to behave like the
!     object they proxy, as much as they can.  Regardless of the
!     underlying type, proxies are not hashable since their ability to
!     act as a weak reference relies on a fundamental mutability that
!     will cause failures when used as dictionary keys -- even if the
!     proper hash value is computed before the referent dies, the
!     resulting proxy cannot be used as a dictionary key since it cannot
!     be compared once the referent has expired, and comparability is
!     necessary for dictionary keys.  Operations on proxy objects after
!     the referent dies cause weakref.ReferenceError to be raised in
!     most cases.  "is" comparisons, type(), and id() will continue to
!     work, but always refer to the proxy and not the referent.
! 
!     The callbacks registered with weak references must accept a single
!     parameter, which will be the weak-ly referenced object itself.
!     The object can be resurrected by creating some other reference to
!     the object in the callback, in which case the weak reference
!     generating the callback will still be cleared but no remaining
!     weak references to the object will be cleared.