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Open shelves fail when Python exits #51181
Description
| BPO | 6932 |
|---|---|
| Nosy | @birkenfeld |
| 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 = 'https://github.com/birkenfeld'
closed_at = <Date 2009-09-17.16:16:19.732>
created_at = <Date 2009-09-17.15:55:56.272>
labels = ['extension-modules', 'type-bug', 'library', 'docs']
title = 'Open shelves fail when Python exits'
updated_at = <Date 2009-09-17.16:16:19.731>
user = 'https://bugs.python.org/lehmannro'bugs.python.org fields:
activity = <Date 2009-09-17.16:16:19.731>
actor = 'georg.brandl'
assignee = 'georg.brandl'
closed = True
closed_date = <Date 2009-09-17.16:16:19.732>
closer = 'georg.brandl'
components = ['Documentation', 'Extension Modules', 'Library (Lib)']
creation = <Date 2009-09-17.15:55:56.272>
creator = 'lehmannro'
dependencies = []
files = ['14912', '14913']
hgrepos = []
issue_num = 6932
keywords = ['patch']
message_count = 2.0
messages = ['92773', '92776']
nosy_count = 2.0
nosy_names = ['georg.brandl', 'lehmannro']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue6932'
versions = ['Python 3.1', 'Python 2.7']
Activity
lehmannro commentedon Sep 17, 2009
I'm reopening bpo-5483 by Zhigang Wang (zhigang) as a separate bug.
Shelves that are still open when Python terminates will try to sync. If
writeback=True, this pickles cached items.
In this example, serialization of Test() re-imports __main__, which is
already gc'd, and raises:
Exception cPickle.PicklingError: Can't pickle <class '__main__.Test'>:
it's not the same object as __main__.Test" in <bound method
Shelf.__del__ of {'a': <main.Test object at 0x...>}>
The error is ignored (due to Python already tearing down) but all cached
modifications are lost.
The promise "[t]he __del__() method of the Shelf class calls the close()
method, so the programmer generally need not do this explicitly" is not
true with writeback enabled.
I'm unsure if this error can be fixed (probably with atexit/weakref, but
that's more trouble than gain). I attached a patch to the docs simply
warning the user of this issue (+ documenting Shelf.close, + removing
above quote).
birkenfeld commentedon Sep 17, 2009
Fixed docs (a bit differently) in r74876.