Paul Rubin wrote: > Steve Holden <[EMAIL PROTECTED]> writes: > >>>All joking aside, when I have names (temporary variables or scaffolding >>>functions) that I need to initialise a module or data structure, but then >>>outlive their usefulness, I del the name afterwards. Am I the only one? I >>>can't say I've seen anyone else doing that, and it feels icky to me (for >>>no reason I can put my finger on) -- what do others think? > > > I do that too sometimes. I think it's a Python weakness that you > can't declare a local var like in other languages, to go out of scope > at the end of the current block, e.g.: > > if cond: > my x = 7 # make a new scope for x, goes out of scope at end of if > If this genuinely troubles you then you can always isolate the scope with a function, though of course you also no longer have the code inline then.
> >>I don't generally speaking see the point: unless the name is >>referencing something potentially large (like the results of a >>database query) and won't be going out of scope soon (which typically >>happens at the end of the current method or function) I just leave it >>to happen automatically. If it doesn't happen (because the name exists >>at module scope) thwn what the heck. > > > Well, that makes the code a little bit confusing. If you say > > x = some_intermediate_result(...) > do_something_with (x) > > do you know for sure whether x will be needed again? Yes. > Are you sure you > didn't use the name x further up in the function for something that's > still needed? > Yes. Of course, otherwise I wouldn't have used it here, would I? Meaningful names are the biggest help in avoiding errors like this. Are you trying to suggest my memory's going? ;-) > This is one of the areas where there's tension between Python the > scripting language, that gains by saving a few keystrokes when > throwing together a quick hack, and Python the language for developing > long-lasting applications that have to be maintained by multiple people. > > In Haskell you can even have temporary variables inside an expression: > > x = y + y*y + 3 where y=5 > > sets x to 33. I believe (not absolutely sure) that the scope of y is > limited to that expression. Well, as warts go the inability to tightly control the scope of variables isn't really that terrible, is it? regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC www.holdenweb.com PyCon TX 2006 www.python.org/pycon/ -- http://mail.python.org/mailman/listinfo/python-list
