You can define new exceptions of your own that are specific to your programs.
User-defined exceptions are coded with classes, which inherit from a built-in exception class: usually the class named Exception:
class AlreadyGotOne(Exception): pass # User-defined exception # w w w . ja v a 2 s . c o m def grail(): raise AlreadyGotOne() # Raise an instance try: grail() except AlreadyGotOne: # Catch class name print('got exception')