How to Use atexit in Python for Cleanup Actions

Use the atexit module in Python to register functions that you want to run automatically when your program ends. Call atexit.register(your_function) to add a cleanup function that runs on normal program termination.

Syntax

The atexit module provides a simple way to register functions that will be called when the Python program is about to exit normally.

Key parts:

• atexit.register(function, *args, **kwargs): Registers a function to be called with optional arguments when the program exits.
• The registered functions run in the reverse order of their registration.

python

import atexit

def cleanup():
    print('Cleaning up before exit')

atexit.register(cleanup)

Example

This example shows how to register multiple functions with atexit. They will run automatically when the program finishes.

python

import atexit

def goodbye():
    print('Goodbye!')

def cleanup_temp_files():
    print('Removing temporary files...')

atexit.register(cleanup_temp_files)
atexit.register(goodbye)

print('Program is running...')

Output

Program is running...
Goodbye!
Removing temporary files...

Common Pitfalls

What can go wrong:

• Functions registered with atexit only run on normal program exit, not if the program crashes or is killed.
• Exceptions in registered functions are ignored but printed to stderr, so errors might be missed.
• Registering functions that depend on resources already closed can cause errors.

Wrong way: Registering a function that raises an exception without handling it.

Right way: Handle exceptions inside the registered function to avoid silent failures.

python

import atexit

def faulty_cleanup():
    raise Exception('Oops!')

atexit.register(faulty_cleanup)
print('Exiting program...')

Output

Exiting program...
Exception ignored in: <function faulty_cleanup at 0x7f8c2c0d1ee0>
Traceback (most recent call last):
  File "<stdin>", line 4, in faulty_cleanup
Exception: Oops!

Quick Reference

Function	Description
atexit.register(func, *args, **kwargs)	Register a function to be called on program exit
Registered functions run in reverse order	Last registered runs first
Functions run only on normal exit	Not called on crashes or kill signals
Exceptions in registered functions	Are printed but do not stop exit process

Key Takeaways

Use atexit.register() to run cleanup functions automatically when your program ends.

Registered functions run in reverse order of registration.

atexit functions only run on normal program exit, not on crashes or forced termination.

Handle exceptions inside your atexit functions to avoid silent errors.

atexit is useful for closing resources or saving state before the program exits.