returning an error code

[Gribouillis]

Nothing is simpler than writing your own exception

class MyException(RuntimeError):
    pass
class MySubException(MyException):
    pass

raise MySubException('That file is too large!')

The drawback of returning an error code is that it forces the caller to check the error code. On the other hand, if a function raises exceptions, you can just call the function and let the exceptions propagate.