Hi everyone, Based on some earlier list advice, I went back to the drawing board and started testing various approaches to adding the "flyweight" pattern to my classes.
To recap, I have a bunch of campaign finance-related classes and subclasses (Committee, HouseCommittee, PresidentialCommittee, Candidate, CampaignReport, etc.), and I'm trying to add in the ability for a class to check for a unique instance of itself before creating a new instance. So if I have a committee named "Pac1", I want to check if that committee has previously been created. If it does exist, I want to return the "Pac1" instance; otherwise, I want to create the "Pac1" instance. The closest description I could find to this pattern was the "flyweight" (described here: http://www.suttoncourtenay.org.uk/duncan/accu/pythonpatterns.html#behavioural-patterns), though it appears that this pattern relates as much (or more?) to efficient memory usage than to the notion of only creating a new instance if an identical one does not already exist. (If there's a name for the latter piece of this pattern, please let me know so I can avoid typing that phrase over and over again!) I pasted my test code for two approaches to solving this problem, one using a Mixin class and another using Inheritance. http://pastebin.com/m3252c407 I'm not certain I'll need this functionality on all occasions, and not all of my classes/subclasses require this behavior. Given those requirements, is the Mixin approach the way to go? Either way, have I implemented these correctly? Also, for purposes of the test, please note that I commented out the weakref usages (which kind of defeats the purpose of the flyweight pattern, right?). It was easier to wrap my brain around this when the instance ids remained the same. I found that when using weakref, the ids changed (even for what should have been the same instance). Is that due to the nature of how garbage collection works with weakref? Or perhaps I'm not implementing this pattern correctly? Hence my asking you all! As always, any and all advice is appreciated. Serdar _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
