New submission from Kevin M <syl...@gmail.com>:
I've noticed an issue (or user error) in which Python a call that otherwise
usually works in the __del__ step of a class will freeze when the Python
interpreter is exiting.
I've attached sample code that I've ran against Python 3.9.1 on Windows 10.
The code below runs a process and communicates via the pipe.
class SubprocTest(object):
def run(self):
print("run")
proc_args = ["cmd.exe"]
self._process = subprocess.Popen(proc_args,
stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
def __del__(self):
print("__del__")
if self._process is not None:
self.terminate()
def terminate(self):
print("terminate")
self._process.communicate(input=b"exit\n", timeout=1)
print("kill")
self._process.kill()
self._process = None
if __name__ == "__main__":
s = SubprocTest()
s.run()
del s
print("s done")
t = SubprocTest()
t.run()
print("t done")
Current output:
run
__del__
terminate
kill
s done
run
t done
__del__
terminate
<<<<<< hangs indefinitely here, even though timeout=1
Expected output:
run
__del__
terminate
kill
s done
run
t done
__del__
terminate
kill
In normal circumstances, when you del the object and force a run of __del__(),
the process ends properly and the terminate() method completes.
When the Python interpreter exits, Python calls the __del__() method of the
class. In this case, the terminate() never completes and the script freezes
indefinitely on the communicate()
----------
components: Library (Lib), Windows
files: win_subprocess_hang.py
messages: 390587
nosy: paul.moore, steve.dower, sylikc, tim.golden, zach.ware
priority: normal
severity: normal
status: open
title: [Windows] interpreter hangs indefinitely on subprocess.communicate
during __del__ at script exit
versions: Python 3.9
Added file: https://bugs.python.org/file49947/win_subprocess_hang.py
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<https://bugs.python.org/issue43784>
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