Exceptions' Behaviour

[Martin Sjögren]

I've been fooling around with exceptions a bit today, and found some
things that I don't quite understand.

class A (Exception): pass
class B (Exception): pass

        try:
            raise A, B
        except A, var:
            print "A,", var
        except (A, B), var:
            print "(A,B),", var

This prints 'A, __main__.B'

        try:
            raise A, B
        except (A, B), var:
            print "(A,B),", var
        except A, var:
            print "A,", var

This prints '(A, B), __main__.B'


That's rather predictiable, here comes the funky part:

        try:
            raise (A, B)
        except A, var:
            print "A,", var
        except (A, B), var:
            print "(A,B),", var

This prints 'A, '

        try:
            raise (A, B)
        except (A, B), var:
            print "(A,B),", var
        except A, var:
            print "A,", var

This prints '(A,B), '

!!!
What's going on here? If (A, B) is raised like A, B, why don't I get
anything in my 'var' variable? If not, how come (A, B) is matched against
A?

I'm really confused here...

Martin Sjögren

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Martin Sjögren
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