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Weakref not working properly #45758
Description
| BPO | 1417 |
|---|---|
| Nosy | @birkenfeld, @rhettinger |
| Files |
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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GitHub fields:
assignee = None
closed_at = <Date 2007-11-10.17:44:34.360>
created_at = <Date 2007-11-10.12:20:51.920>
labels = ['invalid', 'type-bug', 'library']
title = 'Weakref not working properly'
updated_at = <Date 2007-11-15.21:21:12.027>
user = 'https://bugs.python.org/MHOOO'bugs.python.org fields:
activity = <Date 2007-11-15.21:21:12.027>
actor = 'MHOOO'
assignee = 'none'
closed = True
closed_date = <Date 2007-11-10.17:44:34.360>
closer = 'georg.brandl'
components = ['Library (Lib)']
creation = <Date 2007-11-10.12:20:51.920>
creator = 'MHOOO'
dependencies = []
files = ['8725', '8733', '8744']
hgrepos = []
issue_num = 1417
keywords = []
message_count = 7.0
messages = ['57348', '57353', '57355', '57362', '57375', '57481', '57562']
nosy_count = 5.0
nosy_names = ['georg.brandl', 'rhettinger', 'ggenellina', '_doublep', 'MHOOO']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = None
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue1417'
versions = ['Python 2.5']
Activity
MHOOO commentedon Nov 10, 2007
The following code is not working as expected:
import weakref
class cls1:
def giveTo( self, to ):
to.take( self.bla )
def bla(self ):
pass
class cls2:
def take( self, what ):
self.ref = weakref.ref(what)
c1 = cls1()
c2 = cls2()
c1.giveTo( c2 )
print c1.bla
print c2.ref
It prints out:
<bound method cls1.bla of <main.cls1 instance at 0x00CA9E18>>
<weakref at 00CAF180; dead>
Why is the weakref pointing to a dead object, when it's still alive?
doublep commentedon Nov 10, 2007
Because self.bla is a bound-method object, which is created and then
instantly deleted as unreferenced. This is not a bug, it is expected.
Note how the objects are different.
birkenfeld commentedon Nov 10, 2007
Closing as invalid.
rhettinger commentedon Nov 10, 2007
It's easier to see what is going on if you print the object ids. The
id of self.bla is different than the subsequent c1.bla. The first is
freed before the second gets created.
MHOOO commentedon Nov 11, 2007
Well, too bad.
My workaround (to make weakrefs work) is attached as a file.
ggenellina commentedon Nov 14, 2007
I think this methodref function is simpler and much less intrusive
MHOOO commentedon Nov 15, 2007
Yeah, cool :)
Thanks =)