Exception processing is useful for error handling, termination actions, and event notification. It can also simplify the handling of special cases and can be used to implement alternative control flows. In general, exception processing also cuts down on the amount of error-checking code your program may require—because all errors filter up to handlers, you may not need to test the outcome of every operation.

Any uncaught exception eventually filters up to the default exception handler Python provides at the top of your program. This handler prints the familiar error message and shuts down your program.