priority_queue.py

import heapq

class PriorityQueue:
  def __init__(self):
    self._queue = []
    self._index = 0

  def push(self, item, priority):
    heapq.heappush(self._queue, (-priority, self._index, item))
    self._index += 1

  def pop(self):
    return heapq.heappop(self._queue)[-1]

class Item:
  def __init__(self, name):
    self._name = name

  def __str__(self):
    return "Item(%s)" % (self._name)

if __name__ == '__main__':
  q = PriorityQueue()
  q.push(Item('task1'), 1)
  q.push(Item('task2'), 4)
  q.push(Item('task3'), 2)
  q.push(Item('task4'), 5)
  q.push(Item('task5'), 6)

  assert q.pop(), 'Item(task5)'
  assert q.pop(), 'Item(task4)'
  assert q.pop(), 'Item(task2)'
  assert q.pop(), 'Item(task1)'