New submission from Matt <[email protected]>:
I'm trying to evaluate process' state between two "sibling" processes
(processes created by the same parent process); using the .is_alive() and
exitcode to evaluate whether a process has been init'd, started, finished
successfully or unsuccessfully.
The reference to one process is passed to the other and I'd like to call
.is_alive(). This raises the following assertion error:
Process C-2:
Traceback (most recent call last):
File "/usr/lib/python3.7/multiprocessing/process.py", line 297, in _bootstrap
self.run()
File "/home/timms/.PyCharm2019.2/config/scratches/is_alive_method.py", line
59, in run
print("brother - ",self.brother.state)
File "/home/timms/.PyCharm2019.2/config/scratches/is_alive_method.py", line
16, in state
if self.is_alive():
File "/usr/lib/python3.7/multiprocessing/process.py", line 151, in is_alive
assert self._parent_pid == os.getpid(), 'can only test a child process'
AssertionError: can only test a child process
It's obvious that the assertion fails given the family structure of the
processes. Overwriting the is_alive() method in my own process class appears to
produce my desired output behaviour - with assertion and discarding self
removed (see attachment).
Is there something fundamental to how process' operate that I should be weary
of? I understand that is_alive also joins itself if possible; is that the sole
reason for the assertion? Could a method that mirrors is_alive() without the
assertion and discard method work with the desired intention I've described
above?
----------
files: is_alive_method.py
messages: 358232
nosy: matttimms
priority: normal
severity: normal
status: open
title: multiprocessing is_alive() between children processes
type: behavior
versions: Python 3.7
Added file: https://bugs.python.org/file48770/is_alive_method.py
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Python tracker <[email protected]>
<https://bugs.python.org/issue39021>
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