Map is a common way to transform lists in most programming languages. In Python, map is a function that loops over a list and applies a function (that you provide) to each item. Your function receives ...

Don't let the movie be your first visit to the Borderlands franchise.

A PriorityQueue is a list that always keeps its items sorted based on some rule, like smallest to largest. So, when you take an item out, you always get the one with the highest (or lowest) priority.