Modern Python Standard Library Cookbook

How to do it...

Heaps are a perfect match for everything that has priorities, such as a priority queue:

import time
import heapq

class PriorityQueue:
    def __init__(self):
        self._q = []

    def add(self, value, priority=0):
        heapq.heappush(self._q, (priority, time.time(), value))

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

Then, our PriorityQueue can be used to retrieve entries given a priority:

>>> def f1(): print('hello')
>>> def f2(): print('world')
>>>
>>> pq = PriorityQueue()
>>> pq.add(f2, priority=1)
>>> pq.add(f1, priority=0)
>>> pq.pop()()
hello
>>> pq.pop()()
world