On Tue, Mar 04, 2003 at 10:50:34AM -0800, sean.upton@uniontrib.com wrote:
Thinking aloud: ...so myNonZopeClass instances need to be a singleton-like thing, with some sort of mutex-ish of lock to prevent other instances from being constructed?
singletons seem to be more easily handled by other pythonic approaches, as you go on to say ...
I wonder if there is a way to throw an exception on construction of a myNonZopeClass instance if another Zope thread has an instance. Perhaps you could keep an external boolean lock variable in a module-level global accessible to all threads, but it might just be easier to follow Toby's suggestion and just see if you can keep your myNonZopeClass instance object in a module-level global, and just keep a reference to it in a _v_ attribute? I've never tried anything like this, might something like this possibly work?
I'd think so. Another approach to consider is "Borg" aka "Monostate" aka "all your state are belong to us". http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66531 yet another approach is to use a class instead of a module, e.g. http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/113657 None of these address the issues of access control, as Alex Martelli's comments on Borg make clear: """ threading, Alex Martelli, 2001/10/15 Threading issues really have little to do with Highlander vs Borg (or Singleton vs Monostate if you prefer boring names:-). In Python, it's simplest to devote a thread to handling a bunch of resources that need to be serialized (no matter whether they're wrapped into one or more objects of whatever type), with a Queue of requests on which the devoted-thread (Guardian thread) always sleeps working for requests. All access by working threads to the guardian thread and the resources it protects is by posting to the guardian queue a tuple (response-queue, callable, args, kwds) followed by waiting on the response-queue. Why people would want to conflate this important idiom with the equally important and unrelated idiom of state sharing is a mystery to me, as they work just as well together or separately. What's the contrary of "divide and conquer" -- "conflate and suffer"?-) """ hmmm, i can't quite envision how you'd do this "guardian thread" business in a Zope product, or if there's a better equivalent. -- Paul Winkler http://www.slinkp.com