Suppose that you have code that generates an abstract 'list' of somesort and returns it inside a try:/finally: block. There are two commonways to code this; you can return a real list, or you can use yield tobe a generator. You might even code it one way and change it to the otherlater, which is generally a transparent change.

Not this time, though. If you are using finally: , the two options canhave quite different behavior. Constructing an example

There are at least two ways to set up vacation messages; they cango to the envelope sender (the SMTP MAIL FROM ), or they can go tothe apparent author of the mail message, usually plucked from the From: header. It's my personal view that mailing list managers shouldimmediately unsubscribe people who have the second sort of vacationmessage system.

(I admit that I haven't always had the courage to do this for liststhat I run.)

It's one thing to harass