Joe Strout wrote: > One thing I miss as I move from REALbasic to Python is the ability to > have static storage within a method -- i.e. storage that is persistent > between calls, but not visible outside the method. I frequently use > this for such things as caching, or for keeping track of how many > objects a factory function has created, and so on. > This is a pretty bizarre requirement, IMHO. The normal place to keep such information is either class variables or instance variables.
> Today it occurred to me to use a mutable object as the default value of > a parameter. A simple example: > > def spam(_count=[0]): > _count[0] += 1 > return "spam " * _count[0] > >>>> spam() > 'spam ' >>>> spam() > 'spam spam ' > > This appears to work fine, but it feels a little unclean, having stuff > in the method signature that is only meant for internal use. Naming the > parameter with an underscore "_count" makes me feel a little better > about it. But then, adding something to the module namespace just for > use by one function seems unclean too. > It's a bad smell. > What are your opinions on this idiom? Is there another solution people > generally prefer? > > Ooh, for a change I had another thought BEFORE hitting Send rather than > after. Here's another trick: > > def spam2(): > if not hasattr(spam2,'count'):spam2.count=0 > spam2.count += 1 > return "spam2 " * spam2.count > > This doesn't expose any uncleanliness outside the function at all. The > drawback is that the name of the function has to appear several times > within itself, so if I rename the function, I have to remember to change > those references too. But then, if I renamed a function, I'd have to > change all the callers anyway. So maybe this is better. What do y'all > think? > I think you'd be much better off creating an instance of a class and using that. regards Steve -- Steve Holden +1 571 484 6266 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ -- http://mail.python.org/mailman/listinfo/python-list
