[New-bugs-announce] [issue6634] sys.exit() called from threads other than the main one: undocumented behaviour

[Jan-Philip Gehrcke]

New submission from Jan-Philip Gehrcke <jgehrcke at gmail.com>:

Hey there,

hopefully I fill out this form in an adequate way!

I ran into some problems while using sys.exit('msg') together with
threads, which could have been avoided with slightly more information in
the docs here: http://docs.python.org/library/sys.html#sys.exit 

Maybe the following two statements should not stay as they are:

(1) "Exit from Python."
-----------------------
This is not true when called from a thread other than the main one. We
could add a hint, saying that sys.exit() then actually behaves like
thread.exit(), which causes only the calling thread to exit, but not the
main program.

2) "[...] and any other object is printed to sys.stderr"
--------------------------------------------------------
This is also not true when called from a thread other than the main one.
Calling sys.exit('msg') then doesn't print anything to stderr. That was
annoying in my case and required debugging a bug that would have
discovered itself via stderr, if the message would have been printed..
:-) After some research, I think this behaviour is described in the
documentation for thread.exit(): "[...] this will cause the thread to
exit *silently*."


Okay, now that I am aware of this behaviour, I won't run into these
problems again. But the next one?

I think (1) is clearly a documentation thing. Regarding (2): first of
all, the documentation should say that the message is suppressed in
special cases (child threads). But: what argues against printing to
stderr here? I don't get the point and only see a lost feature,
affording a quick way to kill a thread while dropping an error message.
Was this kicked out intentionally? Maybe someone could help me with a
good argument here :-)


Thank you for your work,

Jan-Philip Gehrcke

----------
assignee: georg.brandl
components: Documentation
messages: 91237
nosy: georg.brandl, jgehrcke
severity: normal
status: open
title: sys.exit() called from threads other than the main one: undocumented behaviour
versions: Python 2.4, Python 2.5, Python 2.6, Python 2.7, Python 3.0, Python 3.1

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue6634>
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