Modern Python Standard Library Cookbook

How it works...

PriorityQueue works by storing everything in an heap. Heaps are particularly efficient at retrieving the top/first element of a sorted set without having to actually sort the whole set.

Our priority queue stores all the values in a three-element tuple: priority, time.time(), and value.

The first entry of our tuple is priority (lower is better). In the example, we recorded f1 with a better priority than f2, which ensures than when we use heap.heappop to fetch tasks to process, we get f1 and then f2, so that we end up with the hello world message and not world hello.

The second entry, timestamp, is used to ensure that tasks that have the same priority are processed in their insertion order. The oldest task will be served first ...