Jan-Philip Gehrcke <jgehrcke@gmail.com> added the comment: Sorry for the delay. Before suggesting a doc change to correct/complete the description of the *current* situation, we actually should consider changing this situation. I think this is reasonable and I feel encouraged by Gabriel Genellina:

I see no reason for sys.exit("msg") NOT to write to stderr inside a child thread.

This patch enables printing to stderr from child threads and clones the behavior of `sys.exit(arg)` called from the main thread: # PATCH BEGIN --- C:/Python27/Lib/threading.py Sat Apr 10 18:55:48 2010 +++ C:/python_sys_exit_issue/threading.py Sat Sep 25 14:50:24 2010 @@ -531,6 +531,15 @@ except SystemExit: if __debug__: self._note("%s.__bootstrap(): raised SystemExit", self) + # Now get and handle the "exit code", given by the user via + # the second expression after `raise` or via the argument of + # sys.exit(). + code = self.__exc_info()[1].code + # Ignore None and integer exit code. Print any other object + # to stderr as it is the behavior of sys.exit(arg) called + # from the main thread. + if code is not None and not isinstance(code, int): + _sys.stderr.write("%s\n" % code) except: if __debug__: self._note("%s.__bootstrap(): unhandled exception", self) # PATCH END A script with different testcases including output is attached. What do you think? All the best, Jan-Philip Gehrcke ---------- Added file: http://bugs.python.org/file19006/thread_sys_exit_test.py _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue6634> _______________________________________