Python Data Analysis Cookbook

Caching with a least recently used cache

Caching involves storing results, usually from a function call, in memory or on disk. If done correctly, caching helps by reducing the number of function calls. In general, we want to keep the cache small for space reasons. If we are able to find items in cache, we talk about hits; otherwise, we have misses. Obviously, we want to have as many hits as possible and as few misses as possible. This means that we want to maximize the hits-misses ratio.

Many caching algorithms exist, of which we will cover the least recently used (LRU) algorithm. This algorithm keeps track of when a cache item was used. If the cache is about to exceed its maximum specified size, LRU gets rid of the least recently used item. The ...