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Open shelves fail when Python exits #51181

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lehmannro mannequin opened this issue Sep 17, 2009 · 2 comments
Closed

Open shelves fail when Python exits #51181

lehmannro mannequin opened this issue Sep 17, 2009 · 2 comments
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@birkenfeld
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docs Documentation in the Doc dir extension-modules C modules in the Modules dir stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error

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@lehmannro
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lehmannro mannequin commented Sep 17, 2009

BPO 6932
Nosy @birkenfeld
Files
  • example.py: minimal example reproducing the error
  • shelve-warning.patch: patch to Doc/library/shelve.rst, trunk
    		•

    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']
    @lehmannro
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    lehmannro mannequin commented 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).

    @lehmannro lehmannro mannequin assigned birkenfeld Sep 17, 2009
    @lehmannro lehmannro mannequin added docs Documentation in the Doc dir extension-modules C modules in the Modules dir stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error labels Sep 17, 2009
    @birkenfeld
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    Fixed docs (a bit differently) in r74876.

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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