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Python shelve __del__ ignored exception #83383

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libbkmz mannequin opened this issue Jan 3, 2020 · 2 comments
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Python shelve __del__ ignored exception #83383

libbkmz mannequin opened this issue Jan 3, 2020 · 2 comments
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@serhiy-storchaka
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3.13 bugs and security fixes stdlib Python modules in the Lib dir type-feature A feature request or enhancement

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@libbkmz
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libbkmz mannequin commented Jan 3, 2020 •
edited by bedevere-app bot
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BPO 39202
Nosy @libbkmz
Files
  • test_python_shelve_issue.py: python testcases via unittests library to reproduce the issue
    		•

    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 = None
created_at = <Date 2020-01-03.16:19:53.484>
labels = ['3.8', 'type-feature', 'library']
title = 'Python shelve __del__ ignored exception'
updated_at = <Date 2020-01-03.16:19:53.484>
user = 'https://github.com/libbkmz'

    bugs.python.org fields:

    activity = <Date 2020-01-03.16:19:53.484>
actor = 'libbkmz'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2020-01-03.16:19:53.484>
creator = 'libbkmz'
dependencies = []
files = ['48826']
hgrepos = []
issue_num = 39202
keywords = []
message_count = 1.0
messages = ['359242']
nosy_count = 1.0
nosy_names = ['libbkmz']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue39202'
versions = ['Python 3.8']

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    @libbkmz
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    libbkmz mannequin commented Jan 3, 2020

    I'm using my own implementation of the memoize by shelve module. In the attachment, there are 2 simple test cases which pass but the console there are a lot of messages like that:

    Exception ignored in: <function Shelf.__del__ at 0x0000023202F363A0>
Traceback (most recent call last):
  File "C:\Miniconda2\envs\38_common\lib\shelve.py", line 162, in __del__
    self.close()
  File "C:\Miniconda2\envs\38_common\lib\shelve.py", line 144, in close
    self.sync()
  File "C:\Miniconda2\envs\38_common\lib\shelve.py", line 172, in sync
    self.dict.sync()
  File "C:\Miniconda2\envs\38_common\lib\dbm\dumb.py", line 129, in _commit
    with self._io.open(self._dirfile, 'w', encoding="Latin-1") as f:
PermissionError: [Errno 13] Permission denied: 'C:\\project\\tests\\test_memoize_tmp_t5tai08p\\memoize_test_file.dat.dir'

Exception ignored in: <function _Database.close at 0x0000023202EF9040>
Traceback (most recent call last):
  File "C:\Miniconda2\envs\38_common\lib\dbm\dumb.py", line 274, in close
    self._commit()
  File "C:\Miniconda2\envs\38_common\lib\dbm\dumb.py", line 129, in _commit
    with self._io.open(self._dirfile, 'w', encoding="Latin-1") as f:
PermissionError: [Errno 13] Permission denied: 'C:\\project\\tests\\test_memoize_tmp_t5tai08p\\memoize_test_file.dat.dir'

    Basically, the main issue can be explained like that - Python dbm.dumb._Database should maintain self._modified the attribute in the right way(set it to False) after the _commit method.

    Later I will try to make changes in the dbm.dumb module and run Python internal tests for that modification to see any regression, if not will add PR here.

    @libbkmz libbkmz mannequin added 3.8 (EOL) end of life stdlib Python modules in the Lib dir type-feature A feature request or enhancement labels Jan 3, 2020
    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
    serhiy-storchaka added a commit to serhiy-storchaka/cpython that referenced this issue Jan 25, 2024
    @serhiy-storchaka
    pythongh-83383: Always mark the dbm.dumb database as unmodified after…
    068d971 
    … open() and sync()

The directory file for a newly created database is now created
immediately after opening instead of deferring this until synchronizing
or closing.
    @bedevere-app bedevere-app bot mentioned this issue Jan 25, 2024
    Merged
    @serhiy-storchaka serhiy-storchaka added 3.13 bugs and security fixes and removed 3.8 (EOL) end of life labels Jan 25, 2024
    @serhiy-storchaka
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    It is not a bug. If you do not close the database explicitly, it will be implicitly closed in the __del__() method. And this happens when the local variable memoize is rebound, which happens only after a new database referring to the same files is opened. Opening multiple databases that use the same files is not supported.

    But it is good idea to mark the database as unmodified after synchronization or creation and avoid any writing in __del__() if there was no modifications since that moment. It helps to save data, even if the use of the database is not perfect.

    @serhiy-storchaka serhiy-storchaka self-assigned this Jan 25, 2024
    serhiy-storchaka added a commit that referenced this issue Feb 4, 2024
    @serhiy-storchaka
    gh-83383: Always mark the dbm.dumb database as unmodified after open(…
    fc06096 
    …) and sync() (GH-114560)

The directory file for a newly created database is now created
immediately after opening instead of deferring this until synchronizing
or closing.
    aisk pushed a commit to aisk/cpython that referenced this issue Feb 11, 2024
    @serhiy-storchaka @aisk
    pythongh-83383: Always mark the dbm.dumb database as unmodified after…
    ce82e49 
    … open() and sync() (pythonGH-114560)

The directory file for a newly created database is now created
immediately after opening instead of deferring this until synchronizing
or closing.
    fsc-eriker pushed a commit to fsc-eriker/cpython that referenced this issue Feb 14, 2024
    @serhiy-storchaka @fsc-eriker
    pythongh-83383: Always mark the dbm.dumb database as unmodified after…
    16baf0e 
    … open() and sync() (pythonGH-114560)

The directory file for a newly created database is now created
immediately after opening instead of deferring this until synchronizing
or closing.
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