LRU Cache Foundation

'Foundation for rolling your own LRU cache variants'

import collections

class LRU:

    def __init__(self, func, maxsize=128):
        self.cache = collections.OrderedDict()
        self.func = func
        self.maxsize = maxsize

    def __call__(self, *args):
        cache = self.cache
        if args in cache:
            cache.move_to_end(args)
            return cache[args]
        result = self.func(*args)
        cache[args] = result
        if len(cache) > self.maxsize:
            cache.popitem(last=False)
        return result

if __name__ == '__main__':

    f = LRU(ord, maxsize=3)
    for c in 'ABCDCE':
        print('%s -> %s\t\t%r' % (c, f(c), f.cache))
    f.cache.pop(('C',), None)          # invalidate 'C'
    print(f.cache)
    f.cache.clear()