The __del__ special method is designed to be called by the Python virtual machine when an object is no longer reachable, but before it is destroyed. Calling a __del__ method explicitly may cause an object to enter an unsafe state.

If explicit clean up of an object is required, a close() method should be called or, better still, wrap the use of the object in a with statement.

In the first example, rather than close the zip file in a conventional manner the programmer has called __del__. A safer alternative is shown in the second example.

Python Standard Library: object.__del__