python sys exit code and message

How to throw error and exit with a custom message in python

stackoverflow.com › questions › 22633544 › how-to-throw-error-and-exit-with-a-custom-message-in-python

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

Answer from lvc on Stack Overflow

Stack Overflow

stackoverflow.com › questions › 22633544 › how-to-throw-error-and-exit-with-a-custom-message-in-python

How to throw error and exit with a custom message in python - Stack Overflow

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1 of 5

178

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

2 of 5

There are 3 approaches, the first as lvc mentioned is using sys.exit

sys.exit('My error message')

The second way is using print, print can write almost anything including an error message

print >>sys.stderr, "fatal error"     # Python 2.x
print("fatal error", file=sys.stderr) # Python 3.x

The third way is to rise an exception which I don't like because it can be try-catch

  raise SystemExit('error in code want to exit')

it can be ignored like this

try:
  raise SystemExit('error in code want to exit')
except:
  print("program is still open")

Stack Overflow

stackoverflow.com › questions › 285289 › exit-codes-in-python

What does "script xyz.py returned exit code 0" mean in Python? - Stack Overflow

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1 of 16

347

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.

2 of 16

151

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.

Discussions

Return vs sys.exit()

Consider a program with threads and lots of asynchronous stuff. I have a main where at the end of it somebody has written “sys.exit(0)”. And in catching exceptions at some places there’s sys.exit(1). But I want to return some data at the end of main. If I use return statement above ... More on discuss.python.org

discuss.python.org

February 5, 2024

Is sys.exit() bad practice?

In a library that someone else uses, if you call sys.exit, you won't be popular. In your own code, it's manageable however you want to handle it More on reddit.com

r/Python

111

February 13, 2018

Python logging sys.exit('message') - Stack Overflow

However, I have a lot of code that was written without proper logging that simply prints an error message before exiting. ... I'd like to know if there's a way to capture those errors, format them in the same way as other errors (with timestamp) and save them in the same a error.log file used ... More on stackoverflow.com

stackoverflow.com

Is it better to quit a script due to a user input error using sys.exit(1) or raise Error()?

I think that's just a style decision; I don't think there is a best practice for that. Personally I'd use the raise option, probably because I like to think people use my scripts in their scripts, and the raise option allows them to catch it easier. More on reddit.com

r/learnpython

December 9, 2022

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Python

docs.python.org › 3 › library › sys.html

sys — System-specific parameters and functions

Some systems have a convention ... 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....

Piccolo-orm

piccolo-orm.com › blog › understanding-sys-exit

Understanding sys.exit - Piccolo Blog

April 21, 2021 - The number passed to sys.exit is the exit code. In Unix, an exit code of 1 means something went wrong. An exit code of 0 means it was successful. On the command line, you can see the exit code of the last command using echo $?. >>> python successful_script.py >>> echo $? 0 >>> python ...

GeeksforGeeks

geeksforgeeks.org › python › python-exit-commands-quit-exit-sys-exit-and-os-_exit

Python exit commands: quit(), exit(), sys.exit() and os._exit() - GeeksforGeeks

July 12, 2025 - Example: In the given code, the sys.exit("Age less than 18") line will terminate the Python script with a message "Age less than 18" if the variable age is less than 18. If age is 18 or greater, it will print "Age is not less than 18".

Python.org

discuss.python.org › python help

Return vs sys.exit() - Python Help - Discussions on Python.org

Top answer

1 of 9

From where is your main function being called? That is what really matters. In general, no, wirting sys.exit() and return are not the same thing. But yes, putting anything in a function after a return statement is completely useless and that code will never be executed.

2 of 9

@MegaIng at the end of this python script main() is called if __ name __ is main, which is indirectly a shell script that calls it. And I want to return data in that shell script. My doubt is sys.exit at the end of main or end of everything is same as return right?

reddit.com › r/python › is sys.exit() bad practice?

Is sys.exit() bad practice? : r/Python

February 13, 2018 - The idea is that if there is an (unhandled) exception, it exits and displays it without throwing all of the python muck to the screen. I also often add a hidden flag to instead raise the original exception so that I can better debug ... I just do something like raise SystemExit(3) when I want ...

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Stack Overflow

stackoverflow.com › questions › 30387269 › python-logging-sys-exitmessage

Python logging sys.exit('message') - Stack Overflow

Top answer

1 of 1

Since sys.exit is implemented by raising the SystemExit exception, you can catch the exception and log it:

import logging
import sys
import os

logging.basicConfig(level=logging.DEBUG)
logger = logging.getLogger('example')

def function_will_exit():
    sys.exit('some error log')

try:
    function_will_exit()
except SystemExit as e:
    # this log will include traceback
    logger.exception('function_will_exit failed with exception')
    # this log will just include content in sys.exit
    logger.error(str(e))

    # if you don't need exception traceback from Python
    # os._exit(1)
    raise

Python Morsels

pythonmorsels.com › exiting-a-python-program

Exiting a Python program - Python Morsels

February 21, 2022 - When sys.exit is called with a string, Python prints that string and exits with the code 1. $ python3 fixme.py /home/unicorn && echo "Success" /home/unicorn is not a directory

Tutorialspoint

tutorialspoint.com › python › python_sys_exit_method.htm

Python sys.exit() method

The message will be printed to stderr − · import sys if len(sys.argv) < 2: sys.exit("No arguments provided. Exiting the program.") print("Arguments provided. Continuing the program.") No arguments provided. Exiting the program. This example prompts the user to enter a positive number. If a negative number is entered it raises a ValueError and exits the program with an error message −

Python

bugs.python.org › issue36691

Issue 36691: SystemExit & sys.exit : Allow both exit status and message - Python tracker

This issue tracker has been migrated to GitHub, and is currently read-only. For more information, see the GitHub FAQs in the Python's Developer Guide · This issue has been migrated to GitHub: https://github.com/python/cpython/issues/80872

Notes

henryleach.com › 2025 › 02 › controlling-python-exit-codes-and-shell-scripts

Controlling Python Exit Codes and Shell Scripts - Henry Leach

February 9, 2025 - #!/bin/sh eval python exit-examples.py return_code=$? if [ $return_code = 0 ]; then echo "Success!" elif [ $return_code = 1 ]; then echo "Mild panic!" elif [ $return_code = 42 ]; then echo "Other fallback" else echo "Real Failure" exit $return_code fi · Which might be useful for kicking off other processes, or not, that it's not possible to manage from Python, and would be less error prone than trying to grep messages from stdout in your shell script.

Note.nkmk.me

note.nkmk.me › home › python

How to Exit a Python Program: sys.exit() | note.nkmk.me

April 27, 2025 - $ cat data/temp/stdout.txt $ cat data/temp/stderr.txt Error message ... In the example, the cat command displays the contents of a file on UNIX systems. On Windows, you would use type instead. ... If sys.exit() is called inside a try block, a bare except clause (without specifying the exception type) will catch the SystemExit exception, preventing the program from exiting.

Super Fast Python

superfastpython.com › exit-codes-in-python

Process Exit Codes in Python – SuperFastPython

June 12, 2022 - Recall, setting a string message as an exit code will indicate an unsuccessful exit, setting an exit code of one and reporting the string message on standard error (stderr). We can update the previous example to set a string message when calling sys.exit().

Linux Hint

linuxhint.com › python-exit-codes

Python Exit Codes – Linux Hint

Consider the example below that prints a string instead of an exit code. from sys import exit print("Hi!") exit("Program terminated unexpectedly") print("Welcome to linuxhint") In this case, we are using a string literal as the arg parameter inside the function. Once we run the program: ... We can see that the program prints the message before the exit function and the one in the exit function.

Super Fast Python

superfastpython.com › home › tutorials › exit a process with sys.exit() in python

Exit a Process with sys.exit() in Python - Super Fast Python

September 11, 2022 - It then awakes, reports a message and calls sys.exit() with an exitcode of 1. The child process terminates and the main process wakes up. The status of the child process is reported indicating that it is no longer running (as expected) and that the exit code was 1, as we set when we called sys.exit().

Real Python

realpython.com › ref › builtin-exceptions › systemexit

SystemExit | Python’s Built-in Exceptions – Real Python

Exiting. In this example, you raise SystemExit to end the program with an error message if the age is invalid. ... In this tutorial, you'll get to know some of the most commonly used built-in exceptions in Python.

Abbbi

abbbi.github.io › logging

python logging messages and exit codes

Everyone knows that an application exit code should change based on the success, error or maybe warnings that happened during execution. Lately i came along some python code that was structured the following way: #!/usr/bin/python3 import sys import logging def warnme(): # something bad happens logging.warning("warning") sys.exit(2) def evil(): # something evil happens logging.error("error") sys.exit(1) def main(): logging.basicConfig( level=logging.DEBUG, ) [..]

reddit.com › r/learnpython › is it better to quit a script due to a user input error using sys.exit(1) or raise error()?

r/learnpython on Reddit: Is it better to quit a script due to a user input error using sys.exit(1) or raise Error()?

December 9, 2022 -

Let's say you have a script that is a simple csv parser but the user enters an invalid filepath for the csv.

Is it better to exit the script with a print("wrong filepath") and then sys.exit(1) or by using raise SomeError("wrong filepath")?

From what I read sys.exit(1) raises an exception also, but it doesn't seem to print a traceback like using raise SomeError("wrong filepath") does. So you can just print the message you want the user to see and exit quietly.

If I were to distribute a script like this to public users. What's the better practice?

Top answer

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2 of 3

Doesn't really matter to end-users, although personally I prefer exceptions. sys.exit is technically the same as raise SystemExit, at least close enough.