priority_queue.py

import heapq

class PriorityQueue:
    def __init__(self):
        self.items = []
        self.count = 0

    def enqueue(self, item, priority):
        heapq.heappush(self.items, (priority, self.count, item))
        self.count += 1

    def dequeue(self):
        if not self.is_empty():
            return heapq.heappop(self.items)[2]

    def is_empty(self):
        return len(self.items) == 0

    def size(self):
        return len(self.items)