You're looking for calls to sys.exit(...) (exit(...) calls sys.exit(...)) in the script. The argument to that method is returned to the environment as the exit code.

It's fairly likely that the script is never calling the exit(...) method, and that 0 is the default exit code.

Calling sys.exit with a string will work. The docs mention this use explicitly:

In particular, sys.exit("some error message") is a quick way to exit a program when an error occurs.

To be more specific this will also result in an exit code of 1:

any other object is printed to stderr and results in an exit code of 1

0 and 1 are the exit codes.

exit(0) means a clean exit without any errors / problems

exit(1) means there was some issue / error / problem and that is why the program is exiting.

This is not Python specific and is pretty common. A non-zero exit code is treated as an abnormal exit, and at times, the error code indicates what the problem was. A zero error code means a successful exit.

This is useful for other programs, shell, caller etc. to know what happened with your program and proceed accordingly.

Enjoy this Full Explanation demo.

import subprocess


result = subprocess.run("C:/Windows/System32/WindowsPowerShell/v1.0/powershell.exe Write-Output 'Hello world!' ", shell=True, capture_output=True) # command to run in powershell using python subprocess module

res = result.returncode # return system-exit code of the command

out = result.stdout # return output of the powershell command


print(f"The output of the command is {out}, The exit code is {res} and the process generated by command is {result}.")

output

The output of the command is b'Hello world!\r\n', The exit code is 0 and the process generated by command is CompletedProcess(args="C:/Windows/System32/WindowsPowerShell/v1.0/powershell.exe Write-Output 'Hello world!' ", returncode=0, stdout=b'Hello world!\r\n', stderr=b'').

    

import sys
sys.exit()

This will exit with status code 0; if you don't want that, you can pass a different one or a message:

sys.exit(1)

details from the sys module documentation:

sys.exit([arg])

Exit from Python. This is implemented by raising the SystemExit exception, so cleanup actions specified by finally clauses of try statements are honored, and it is possible to intercept the exit attempt at an outer level.

The optional argument arg can be an integer giving the exit status (defaulting to zero), or another type of object. If it is an integer, zero is considered “successful termination” and any nonzero value is considered “abnormal termination” by shells and the like. Most systems require it to be in the range 0-127, and produce undefined results otherwise. Some systems have a convention for assigning specific meanings to specific exit codes, but these are generally underdeveloped; Unix programs generally use 2 for command line syntax errors and 1 for all other kind of errors. If another type of object is passed, None is equivalent to passing zero, and any other object is printed to stderr and results in an exit code of 1. In particular, sys.exit("some error message") is a quick way to exit a program when an error occurs.

Since exit() ultimately “only” raises an exception, it will only exit the process when called from the main thread, and the exception is not intercepted.

Note that this is the 'nice' way to exit. @glyphtwistedmatrix below points out that if you want a 'hard exit', you can use os._exit(*errorcode*), though it's likely os-specific to some extent (it might not take an errorcode under windows, for example), and it definitely is less friendly since it doesn't let the interpreter do any cleanup before the process dies. On the other hand, it does kill the entire process, including all running threads, while sys.exit() (as it says in the docs) only exits if called from the main thread, with no other threads running.