On Thu, 12 May 2011 15:26:27 -0500, Tycho Andersen wrote: > On Thu, May 12, 2011 at 03:12:39PM -0500, Andrew Berg wrote: >> On 2011.05.12 02:25 PM, MRAB wrote: >> > You can raise an exception wherever you like! :-) >> If I raise an exception that isn't a built-in exception, I get >> something like "NameError: name 'HelloError' is not defined". I don't >> know how to define the exception. > > You'll have to define it, as you would anything else (exceptions are > just regular "things"; in fact you can raise anything that's a class or > instance).
Not quite. >>> raise 42 Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: exceptions must be classes or instances, not int Not a very good error message, because 42 is an instance! >>> isinstance(42, int) True In Python 3, you get a better error message, and further restrictions on what you can raise: >>> raise 42 Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: exceptions must derive from BaseException In general, you should always subclass Exception rather than BaseException. There are, er, exceptions, but for error-handling you normally should inherit from Exception directly, or some sub-class like ValueError, KeyError, etc. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
