[issue19047] Assorted weakref docs improvements

2013-09-22 Thread Roundup Robot 

Roundup Robot added the comment:

New changeset caa16423b324 by Nick Coghlan in branch 'default':
Close #19047: weakref doc cleanups
http://hg.python.org/cpython/rev/caa16423b324

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nosy: +python-dev
resolution:  - fixed
stage: needs patch - committed/rejected
status: open - closed

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[issue19047] Assorted weakref docs improvements

2013-09-22 Thread Richard Oudkerk 

Richard Oudkerk added the comment:

Thanks for the doc cleanup -- I am rather busy right now.

Note that stuff does still get replaced by None at shutdown, and this can still 
produce errors, even if they are much harder to trigger.  If I run the 
following program

import _weakref
import collections

a = hello

class Foo(object):
def __del__(self):
print(a)

collections.foo = Foo()
_weakref.foo = Foo()

then depending on the initial hashseed I get a reproducible error:

$ PYTHONHASHSEED=7 python-release /tmp/bad.py
Exception ignored in: bound method Foo.__del__ of __main__.Foo object at 
0xb733db8c
Traceback (most recent call last):
  File /tmp/bad.py, line 8, in __del__
TypeError: 'NoneType' object is not callable

(Personally I would like to see a flag set late during shutdown which blocks 
__del__ methods from running.)

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[issue19047] Assorted weakref docs improvements

2013-09-19 Thread Nick Coghlan 

Nick Coghlan added the comment:

Changing the title, since I spotted a few other problems as well.

The weakref docs still refer to module globals being set to None during 
shutdown. That is no longer the case. There are also some assumptions about 
cycles with __del__ methods not being garbage collected, which is no longer 
true given PEP 442's improvements to module finalization.

I also realised that the introduction of weakref.finalize and the elimination 
of the set globals to None hack gives Python relatively straightforward 
module destructors [1]:

import weakref, sys
mod = sys.modules[__name__]
def del_this():
# implicit ref to the module globals from the function body
weakref.finalize(mod, del_this)

[1] https://mail.python.org/pipermail/import-sig/2013-September/000748.html

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title: Clarify weakref.finalize objects are kept alive automatically - 
Assorted weakref docs improvements

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[issue19047] Assorted weakref docs improvements

2013-09-19 Thread Antoine Pitrou 

Antoine Pitrou added the comment:

Doc patches certainly welcome :-)

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[issue19047] Assorted weakref docs improvements

2013-09-19 Thread Nick Coghlan 

Nick Coghlan added the comment:

I was initially thinking to myself I have a source checkout right
here, I should just fix it, even though I'm at work and want to go
home... and then I realised the potential scope of the fixes needed,
given the longstanding misbehaviours these docs assume still exist :)

(I also just realised the clone on my work system is ridiculously
stale, so even updating it will likely take a while at this point)

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