Veloz wrote: > On Mar 3, 1:14 am, Gregory Ewing <greg.ew...@canterbury.ac.nz> wrote: >> MRAB wrote: >>> I suppose it depends on the complexity of the data structure. A dict's >>> methods are threadsafe, for example, but if you have a data structure >>> where access leads to multiple method calls then collectively they need >>> a lock. >> It also depends on the nature of the objects being used >> as dict keys. Dict operations invoke the hashing and >> comparison methods of the keys, which in general can >> execute arbitrary Python code. >> >> If the keys are elementary built-in types such as >> strings or ints, then dict operations will *probably* >> be atomic. But I think I'd use a lock anyway, to be >> on the safe side. >> >> -- >> Greg > > Unless I missed where you guys were going, I think we got off the main > point. The main question at hand was this: what's the best way (heck, > any way) to implement a sort of "peek" whereby a number of processes > can write results to some common "object" and some other process can > "peek" into this object, looking for specific items they're interested > in? > > I've tried doing this with a queue, as follows: children all write > results to queue, each result has an identifier. Another interested > party, which wants to know if identifier XXX has been placed in the > queue, removes all the items, one by one from the queue, "keeps" the > one matching the identifier (if found) and puts the rest of the items > back on the queue, so other interested parties can also look through > it. > > This is not a good solution, but it illustrates what I'm trying to > achieve.. > > I'm looking at multiprocessing.Manager, ctypes, etc, but nothing's > really jumped out. > > I also tried creating my own list class which uses locks to provide a > "peek and remove" method, but I don't have a good way to share an > instance of this object across processes. > > Any thoughts would be welcomed! > Michael
Sounds to me like you are using one queue when you should be using several. If a single process wants to distribute information to multiple clients, have a queue for each client. This makes it easy for each client to find out if it has work (if it does its queue is non-empty), Is this helpful, or a red herring? regards Steve -- Steve Holden +1 571 484 6266 +1 800 494 3119 PyCon is coming! Atlanta, Feb 2010 http://us.pycon.org/ Holden Web LLC http://www.holdenweb.com/ UPCOMING EVENTS: http://holdenweb.eventbrite.com/ -- http://mail.python.org/mailman/listinfo/python-list
