On 01May2009 08:37, I wrote: | On 30Apr2009 22:57, MRAB <goo...@mrabarnett.plus.com> wrote: | > The producer could send just one None to indicate that it has finished | > producing. | > Each consumer could get the data from the queue, but if it's None then | > put it back in the queue for the other consumer, then clean up and | > finish. | > When all the consumers have finished, the queue will contain just the | > single None. | | And as it happens I have an IterableQueue class right here which does | _exact_ what was just described. You're welcome to it if you like. | Added bonus is that, as the name suggests, you can use the class as | an iterator: | for item in iterq: | ... | The producer calls iterq.close() when it's done.
Someone asked, so code appended below. Cameron Simpson <c...@zip.com.au> DoD#743 http://www.cskk.ezoshosting.com/cs/ class IterableQueue(Queue): ''' A Queue obeying the iterator protocol. Note: Iteration stops when a None comes off the Queue. ''' def __init__(self, *args, **kw): ''' Initialise the queue. ''' Queue.__init__(self, *args, **kw) self.__closed=False def put(self, item, *args, **kw): ''' Put an item on the queue. ''' assert not self.__closed, "put() on closed IterableQueue" assert item is not None, "put(None) on IterableQueue" return Queue.put(self, item, *args, **kw) def _closeAtExit(self): if not self.__closed: self.close() def close(self): ##logFnLine("%s.close()"%(self,),frame=sys._getframe(1)) if self.__closed: # this should be a real log message print >>sys.stderr, "close() on closed IterableQueue" else: self.__closed=True Queue.put(self,None) def __iter__(self): ''' Iterable interface for the queue. ''' return self def next(self): item=self.get() if item is None: Queue.put(self,None) # for another iterator raise StopIteration return item -- http://mail.python.org/mailman/listinfo/python-list
