Cleanup Logic with try/except/finally

This lesson covers cleanup logic with try/except/finally, so you can write code that reliably runs regardless of whether an error occurred. It's written for anyone searching "Python finally tutorial".

A finally block is a cleanup block that always runs, whether or not an exception occurred. Use it whenever you want to guarantee that "this one piece of cleanup happens no matter what." Cleanup work — closing a file, ending a network connection — needs to run reliably regardless of whether an error occurred.

The sample code's divide function has a try block that does the calculation, an except block that handles errors, and a finally block that always displays "Finishing calculation" no matter what. Confirm that the finally message appears both when the division succeeds and when it errors.

A common beginner mistake is writing a return inside finally. Doing so silently overwrites whatever the try block was going to return — something that can lead to unintended behavior. Think of finally purely as a place for cleanup, not for controlling the return value.

finally is commonly used whenever you need to guarantee that a resource gets released, like a database connection or a network call. In real development, gathering the "must happen either way" logic — closing a connection, closing a file — into finally avoids duplicating that logic everywhere.