On Thu, Nov 13, 2008 at 11:16 AM, Joe Strout <[EMAIL PROTECTED]> 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. > > 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. > > 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? >
Static storage is a way of preserving state. Objects are a way of encapsulating state and behavior. Use an object. -- http://mail.python.org/mailman/listinfo/python-list
