Difference between exit() and sys.exit() in Python

Deep Dive into sys.exit() and exit()

Unravelling sys.exit()

sys.exit() is a gift from the sys module, tailored for the termination of a script. It gives you an option to deliver an exit status code or a message, which can be processed by the operating system or the calling processes. This function shines in the spotlight by raising a SystemExit exception, allowing an opportunity for cleanup before the script ends its journey.

A use case of sys.exit() allowing cleanup:

import sys

try:
    # ... some amazing code ...
    sys.exit('Exiting with style.')
except SystemExit as e:
    print(f'Cleaning up the mess: {e}')
    # Steps to wash the dishes, take out the trash... metaphorically, of course!
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This usage ensures a goodbye note with grace, directing any finally blocks or atexit handlers on their next stop.

The ins and outs of exit()

Meanwhile, exit() is a friendly helper function in the Python interpreter universe, created specifically for interactive Python performances—like gracefully leaving the Python REPL or Jupyter Notebook stage. Just like its peer, it also triggers the SystemExit exception but should not make its way into production scripts. The reason being, it's introduced by the site.py startup script and might not be available in all Python realms.

exit() # Leaves the Python shell in style. "Mic drop moment."
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Being a built-in function gives exit() the perk of not requiring to import any modules. No wonder it's so hospitable in the Python interactive universe!

The specific use case of os._exit()

In the world of child processes, especially after a fork() operation, os._exit() comes into the picture. This function stops the process immediately, not bothering to call cleanup handlers or flush stdio buffers. This function resides in the os module and should be used with care, considering it’s abrupt nature.

Code sample for terminating child processes:

import os

pid = os.fork()
if pid == 0:  # Child process
    os._exit(0)  # Bam! Child process leaves the party early
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When to use what?

The go-to for script development

In the typical scenario of script and application development, sys.exit() is the industry standard. It gives you control over your script's exit status and ensures a graceful exit by triggering any registered cleanup handlers.

The charm for interactive use

Juxtaposing that, if you’re in the realm of interactive environments like the Python REPL or Jupyter notebooks, exit() is your best friend. It's the quickest way to excuse yourself from the Python console.

Those special times

In those specialized scenarios that involve child processes or daemons and require an immediate exit, without triggering any additional scripts or handlers, os._exit() is the right choice.