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.
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.
From the documentation for sys.exit:
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.
One example where exit codes are used are in shell scripts. In Bash you can check the special variable $? for the last exit status:
me@mini:~$ python -c ""; echo $?
0
me@mini:~$ python -c "import sys; sys.exit(0)"; echo $?
0
me@mini:~$ python -c "import sys; sys.exit(43)"; echo $?
43
Personally I try to use the exit codes I find in /usr/include/asm-generic/errno.h (on a Linux system), but I don't know if this is the right thing to do.
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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.
This determines the exit status of the program when it finishes running (generally, 0 for success and 1 for error).
It is not unique to Python, and the exact effect depends on your operating system and how the program is called (though 99% of the time, if you're just running Python scripts, it doesn't matter).