python subprocess custom return code

Question

I'd like to return a value from a python subprocess call corresponding to the kind of error returned. E.g.:

test.py

RETCODE_OK = 0
RETCODE_THING_1_FAILED = 1
RETCODE_THING_2_FAILED = 2

def main():
    return RETCODE_THING_2_FAILED

if __name__ == '__main__':
    main()

Then I'm calling it with subprocess, like so:

>>> import subprocess
>>> proc = subprocess.Popen('python test.py', shell=True)
>>> proc.communicate()
(None, None)
>>> proc.returncode
0

I'd like this to return whatever was returned in main(), in this case 2. I've also got other stuff in the stdout and stderr streams, so I can't just print RETCODE_THING_2_FAILED and get the stdout.

Chen A. · Accepted Answer · 2018-03-28T16:04:05.540

Processes uses exit codes, not return statements. You should use sys.exit(STATUS) rather than return STATUS statement:

test2.py:
---------
import sys

def main():
    sys.exit(RETCODE_THING_2_FAILED)

if __name__ == '__main__':
    main()

interpreter:
------------
>>> p = subprocess.Popen('python test2.py')
>>> p.communicate()
(None, None)
>>> p.returncode
2

This is because the process is actually closing/exiting, not returning a value to another function.

python subprocess custom return code

1 Answers1