Exit hanlder for function

at_function_exit.py

# SPDX-FileCopyrightText: 2025 geisserml <[email protected]>
# SPDX-License-Identifier: Apache-2.0 OR BSD-3-Clause

import functools

class finally_decorator:
    
    def __init__(self, callback):
        self._callback = callback
    
    def __call__(self, func):
        @functools.wraps(func)
        def wrapped(*args, **kwargs):
            try:
                return func(*args, **kwargs)
            finally:
                self._callback()
        return wrapped

@finally_decorator(lambda: print("Exit test"))
def test(arg, kwarg=1):
    print(f"Enter test({arg}, {kwarg})")

test(0)

This avoids having a try/finally or with block in the function itself (useful for long function content).

Otherwise, you could do this manually:

def _test_impl():
    print("Long implementation here ...")

def test():
    try:
        _test_impl()
    finally:
        print("Exit handler")

My initial motivation for this was to clean up global state, but refactoring to avoid globals in the first place turned out to be the better solution in that case.

Higher-level solution for globals cleanup: https://gist.github.com/mara004/c1ad00953cf9f4946f45b6dcc9d4778e