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- class PriorityQueue(object):
- """A priority queue implemented using multiple internal queues (typically,
- FIFO queues). The internal queue must implement the following methods:
-
- * push(obj)
- * pop()
- * close()
- * __len__()
-
- The constructor receives a qfactory argument, which is a callable used to
- instantiate a new (internal) queue when a new priority is allocated. The
- qfactory function is called with the priority number as first and only
- argument.
-
- Only integer priorities should be used. Lower numbers are higher
- priorities.
-
- startprios is a sequence of priorities to start with. If the queue was
- previously closed leaving some priority buckets non-empty, those priorities
- should be passed in startprios.
-
- """
-
- def __init__(self, qfactory, startprios=()):
- self.queues = {}
- self.qfactory = qfactory
- for p in startprios:
- self.queues[p] = self.qfactory(p)
- self.curprio = min(startprios) if startprios else None
-
- def push(self, obj, priority=0):
- if priority not in self.queues:
- self.queues[priority] = self.qfactory(priority)
- q = self.queues[priority]
- q.push(obj) # this may fail (eg. serialization error)
- if self.curprio is None or priority < self.curprio:
- self.curprio = priority
-
- def pop(self):
- if self.curprio is None:
- return
- q = self.queues[self.curprio]
- m = q.pop()
- if len(q) == 0:
- del self.queues[self.curprio]
- q.close()
- prios = [p for p, q in self.queues.items() if len(q) > 0]
- self.curprio = min(prios) if prios else None
- return m
-
- def close(self):
- active = []
- for p, q in self.queues.items():
- if len(q):
- active.append(p)
- q.close()
- return active
-
- def __len__(self):
- return sum(len(x) for x in self.queues.values()) if self.queues else 0
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