Exit codes in Python

For the record, you can use POSIX standard exit codes defined here.

Example:

import sys, os

try:
    config()
except:
    sys.exit(os.EX_CONFIG) 
try:
    do_stuff()
except:
    sys.exit(os.EX_SOFTWARE)
sys.exit(os.EX_OK) # code 0, all ok

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.

You're looking for calls to 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.