Question

In the Python docs,

The lowest valued entries are retrieved first (the lowest valued entry is the one returned by sorted(list(entries))[0]). A typical pattern for entries is a tuple in the form: (priority_number, data).

It appears the queue will be sorted by priority then data, which may not be always correct. Suppose data “item 2”, is enqueued before “item 1”, item 1 will still go first. In another docs page, heapq, it suggests the use of a counter. So I will store my data like entry = [priority, count, task]. Isn’t there something like

PriorityQueue.put(item, priority)

Then I won’t need to implement the ordering myself?

Answer 1

As far as I know, what you’re looking for isn’t available out of the box. Anyway, note that it wouldn’t be hard to implement:

from Queue import PriorityQueue

class MyPriorityQueue(PriorityQueue):
    def __init__(self):
        PriorityQueue.__init__(self)
        self.counter = 0

    def put(self, item, priority):
        PriorityQueue.put(self, (priority, self.counter, item))
        self.counter += 1

    def get(self, *args, **kwargs):
        _, _, item = PriorityQueue.get(self, *args, **kwargs)
        return item


queue = MyPriorityQueue()
queue.put('item2', 1)
queue.put('item1', 1)

print queue.get()
print queue.get()

Example output:

item2
item1