AQA 7517 4.1.1.9: Exception handling
The free BugBot lessons that teach this point, a robot to try it on, and the past-paper questions that test it.
What it covers
At GCSE you met runtime errors (F1.4) and validated input before using it (F6.1). A runtime error in Python is an exception: an object that describes what went wrong, raised at the moment it happens. If nothing handles it, the program stops and prints a message. On a laptop that is annoying; on a robot it can mean the motors are left running while the program that should stop them has ended. Exception handling lets a program catch an exception, deal with it, and carry on or shut down safely.
- An unhandled exception
- try and except
- else, finally and as
- Raising your own
- Exceptions or checks?
Or do it in the simulator, with tasks that mark themselves
Lessons that teach it
- A1.3 Exception handling Programming techniques and object-oriented programming
try, except, else and finally, raising your own exceptions, and keeping the motors safe when something goes wrong. - A1.10 Project: the behaviour controller Programming techniques and object-oriented programming
Get past a wall to the dock with prioritised behaviour classes, a controller that aggregates them, and an exception to finish.
Try it on a robot
The task from A1.3 Exception handling, running here. Change the program and press Run.
The specification is AQA's own document; this page says which of our lessons teach point 4.1.1.9 and is not endorsed by the board.