The most common use for __del__() is to ensure that files are closed.

Generally, class definitions that open files will have something like what's shown in the following code:

__del__ = close 

This will ensure that the __del__() method is also the close() method. When the object is no longer needed, the file will be closed, and any operating system resources can be released.

Anything more complex than this is better done with a context manager. See Chapter 6, Using Callables and Contexts, for more information on context managers.