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document behavior of calling atexit.register() while atexit._run_exitfuncs is running #67056

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#104473
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document behavior of calling atexit.register() while atexit._run_exitfuncs is running#67056
#104473
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docsDocumentation in the Doc dir

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@smontanaro
smontanaro
opened on Nov 13, 2014
BPO 22867
Nosy @smontanaro, @vadmium

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 2014-11-13.20:52:37.164>
labels = ['docs']
title = 'document behavior of calling atexit.register() while atexit._run_exitfuncs is running'
updated_at = <Date 2015-07-21.07:43:20.900>
user = 'https://github.com/smontanaro'

bugs.python.org fields:

activity = <Date 2015-07-21.07:43:20.900>
actor = 'ethan.furman'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2014-11-13.20:52:37.164>
creator = 'skip.montanaro'
dependencies = []
files = []
hgrepos = []
issue_num = 22867
keywords = []
message_count = 2.0
messages = ['231135', '231354']
nosy_count = 3.0
nosy_names = ['skip.montanaro', 'docs@python', 'martin.panter']
pr_nums = []
priority = 'low'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue22867'
versions = []

Linked PRs

Activity

  1. smontanaro commented on Nov 13, 2014

    @smontanaro
    smontanaro
    on Nov 13, 2014
    ContributorAuthor

    A discussion on comp.lang.python about prettying up the "if __name__ == 'main__'" idiom led to a suggestion that a decorator could simple register the main function using atexit.register. That looks like it will work, but leaves open the possibility that while main() is running via atexit._run_exitfuncs, other exit functions might be registered.

    As currently defined (at least in the Python version with 2.7), I think everything will work fine. Still, the behavior of adding new exit functions during exit is not defined. Would be kind of nice if this behavior was blessed, and then mentioned in the documentation.

  2. smontanaro
    assigned
    docspython
    on Nov 13, 2014
  3. smontanaro
    added
    docsDocumentation in the Doc dir
    on Nov 13, 2014

  4. ethanfurman commented on Nov 19, 2014

    @ethanfurman
    ethanfurman
    on Nov 19, 2014
    Member

    From a post by Ian Kelly (https://mail.python.org/pipermail/python-list/2014-November/681073.html)
    --------------------------------------------------------------
    In fact it seems the behavior does differ between Python 2.7 and Python 3.4:

    $ cat testatexit.py
import atexit

@atexit.register
def main():
  atexit.register(goodbye)

@atexit.register
def goodbye():
  print("Goodbye")
$ python2 testatexit.py
Goodbye
Goodbye
$ python3 testatexit.py
Goodbye
  5. ezio-melotti
    transferred this issue fromon Apr 10, 2022

  6. iritkatriel commented on May 13, 2023

    @iritkatriel
    iritkatriel
    on May 13, 2023
    Member

    The atexit functions are invoked in LIFO order, so I think it's not a good idea to add more after the first one started running. We don't currently forbid, it and I wouldn't argue in favour of doing so, but we shouldn't encourage it.

  7. smontanaro commented on May 13, 2023

    @smontanaro
    smontanaro
    on May 13, 2023
    ContributorAuthor

    This has been idle for "awhile." Should we just put our heads together and decide how best to document this behavior?

  8. iritkatriel commented on May 13, 2023

    @iritkatriel
    iritkatriel
    on May 13, 2023
    Member

    I'm not sure what the behaviour is. Or rather, what behaviour we want to commit to.

  9. smontanaro commented on May 14, 2023

    @smontanaro
    smontanaro
    on May 14, 2023
    ContributorAuthor

    I'm not sure that committing to any particular behavior is the right thing to do without some more discussion. Maybe just warn that calling atexit.register after _PyAtExit_Call has been invoked is undefined. There's no mention of that corner case in the 3.11 or 3.12 documentation as it stands.

  10. iritkatriel
    added 2 commits that reference this issue on May 14, 2023

    pythongh-67056: document that registering/unregistering an atexit fun…

    d3127cd

    Revert "pythongh-67056: document that registering/unregistering an at…

    e23c17b
  11. iritkatriel
    closed this as completedin #104473on May 15, 2023
  12. iritkatriel
    added a commit that references this issue on May 15, 2023

    gh-67056: document that registering/unregistering an atexit func from…

    b15a1a6
  13. miss-islington
    added a commit that references this issue on May 15, 2023

    pythongh-67056: document that registering/unregistering an atexit fun…

    6ade9ea
  14. iritkatriel
    added a commit that references this issue on May 15, 2023

    [3.11] gh-67056: document that registering/unregistering an atexit fu…

    a712c5f
  15. carljm
    added 2 commits that reference this issue on May 15, 2023

    Merge branch 'main' into supermon

    343867a

    Merge branch 'main' into cached_property_docs

    452d9f5
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