LRU Cache

lrucache.py

class LRUCache(object):
    """ Implements a least-recently-used cache in Python

    As the cache grows it will cap at some fixed size described by the max_size
    property

    When you attempt to add a new object into a full cache, it will discard the
    Least Recently Used cached item.

    Calling set('key', ...) or get('key') constitutes a "use" of 'key'

    Usage:
        cache = LRUCache()
        cache.set('foo', some_complex_object())
        print cache.get('foo')
    """

    def __init__(self, max_size=10):
        self.max_size = max_size
        self.cache = {}
        self.order = []

    def set(self, key, value):
        current_size = len(self.order)
        if self.max_size >= current_size:
            del self.cache[self.order(current_size)]
            del self.order[current_size]
        self.cache[key] = value
        self.order.insert(0, key)

    def get(self, key):
        if key in self.cache:
            self.order.insert(0, key)
            return self.cache[key]
        return None