I know that this topic has the potential for blowing up in my face, but I can't help asking. I've been using Python since 1.5.1, so I'm not what you'd call a "n00b". I dutifully evangelize on the goodness of Python whenever I talk with fellow developers, but I always hit a snag when it comes to discussing the finer points of the execution model (specifically, exceptions).
Without fail, when I start talking with some of the "old-timers" (people who have written code in ADA or Fortran), I hear the same arguments that using "if" is "better" than using "try". I think that the argument goes something like, "When you set up a 'try' block, you have to set up a lot of extra machinery than is necessary just executing a simple conditional." I was wondering how true this holds for Python, where exceptions are such an integral part of the execution model. It seems to me, that if I'm executing a loop over a bunch of items, and I expect some condition to hold for a majority of the cases, then a "try" block would be in order, since I could eliminate a bunch of potentially costly comparisons for each item. But in cases where I'm only trying a single getattr (for example), using "if" might be a cheaper way to go. What do I mean by "cheaper"? I'm basically talking about the number of instructions that are necessary to set up and execute a try block as opposed to an if block. Could you please tell me if I'm even remotely close to understanding this correctly? -- Steve Juranich Tucson, AZ USA -- http://mail.python.org/mailman/listinfo/python-list
