Perl To Python Migration

CREATING NEW EXCEPTION CLASSES

You can create your own exception classes simply by creating a new class which should be set to inherit from one of the existing exception classes. Alternatively, for backwards compatibility, you can also create a string-based exception, for example:

CustomError = 'Error'

raise CustomError

Note that exceptions match against values, thus raising a string exception, but checking against the object will still work:

CustomError = 'Error'

def test():
    raise 'Error'

try:
    test()
except CustomError:
    print "Error!"

However, it's bad practice to rely on this, so you should instead raise one of the predefined error strings.

If you want to create class-based exceptions create a new class, including any initialization information. ...