exit.md

Python by Example: Exit

Programs exit with a status code: 0 means success, non-zero usually means an error. Use sys.exit(code) to exit explicitly. The shell and other programs use this code to detect failures. You can pass an integer or a string—a string is printed to stderr and exits with 1.

What you'll learn:

• sys.exit(0) for success
• sys.exit(1) or higher for errors
• Checking the exit code with echo $? (Unix) or echo %ERRORLEVEL% (Windows)

import sys

# Exit with error code for certain conditions
if "--fail" in sys.argv:
    print("Exiting with error")
    sys.exit(1)

# Normal end of script
print("Program completed")
sys.exit(0)

Exiting with 0 tells the caller the program succeeded. Exiting with 1 or another non-zero value signals failure. Scripts and CI systems use this to decide whether a command succeeded.

To run this program:

$ python source/exit.py
Program completed
$ echo $?
0

$ python source/exit.py --fail
Exiting with error
$ echo $?
1

Tip: Use meaningful exit codes (e.g., 1 for general error, 2 for invalid input) if your script is part of a pipeline.

Try it: Run the script and check the exit code. In a shell script, use if python source/exit.py; then echo OK; else echo Failed; fi.

Source: exit.py

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