Run Cleanup Code on Exit With Python's atexit

Real Python · Beginner ·🔧 Backend Engineering ·3mo ago

Key Takeaways

The video demonstrates how to use Python's atexit module to run cleanup code on exit, including registering functions and handling exceptions.

Full Transcript

Sometimes when your program exits, you want to run some clean-up code. And [clears throat] depending on your program, you might be able to do that when the user hits the quit button, but there is another way. The at exit module allows you to register one or more functions to be called when the program exits. This is done by passing a function reference into at exits register handler call. When your code is done, Python calls the registered function for you. A few caveats. First, this doesn't get called if there's an exception. Doesn't get called if someone control sees your program, or if the exit is triggered by OS exit. So, it's useful for clean exits, but not for messy ones. There are ways of trapping interrupt signals like control C, so you could write a signal handler as well as the at exit handler. Second, the at exit takes a reference to a function, which means the function can't take arguments. But, the functools module has a feature called partials that allows you to wrap functions with a reference, getting around this restriction.

Original Description

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The atexit module in Python allows you to run cleanup code when your program exits. You can register one or more functions to be called when the program exits, but there are some caveats to consider, such as exceptions and interrupt signals.

Key Takeaways

Import the atexit module
Define a cleanup function
Register the cleanup function with atexit.register
Use functools.partial to pass arguments to the cleanup function if needed

💡 The atexit module is useful for clean exits, but not for messy ones, and you may need to use signal handlers to trap interrupt signals like control C.

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