a cache for method

cache.py

#!/usr/bin/python

import functools
from threading import RLock
import logging


class CacheNullValue(object):
    pass

_Null = CacheNullValue()

class Cache(object):

    def __init__(self, cache_limit=1000):
        self._cache = {}
        self._queue = []
        self.cache_limit = cache_limit
        self._lock = RLock()

    def __getitem__(self, name):
        with self._lock:
            return self._cache.get(name, _Null)
    get = __getitem__

    def __setitem__(self, name, value):
        with self._lock:
            if len(self._queue) >= self.cache_limit:
                del self._cache[self._queue.pop()]
            self._queue.append(name)
            self._cache[name] = value
    set = __setitem__


def cache(cache_limit):
    """A function decorator for method cache store
    """
    
    def cached(f):
        @functools.wraps(f)
        def _cached(*args, **kwargs):
            cid = repr((args, kwargs))
            data = _cached.cache.get(cid)
            if data != _Null:
                logging.debug('hit cached `' + _cached.__name__ + '` for ' + cid)
                return data
            data = _cached.f(*args, **kwargs)
            _cached.cache.set(cid, data)
            return data

        _cached.f = f
        _cached.cache = Cache(cache_limit)

        return _cached

    return cached


def setup(cache_limit):
    """ A global thread safe key-value store
    """
    global _cache_object
    _cache_object = Cache(cache_limit)


def set(cid, data):

    _cache_object.set(cid, data)


def get(cid):
    return _cache_object.get(cid)


if __name__ == '__main__':

    logging.basicConfig(level=logging.DEBUG,
                        format='%(asctime)s %(levelname)-8s %(message)s',
                        datefmt='%Y-%m-%d %H:%M:%S', filemode='a+')

    class T(object):

        @cache(100)
        def c(self, t):
            return t

    @cache(100)
    def cc(t):
        return t

    t = T()
    print t.c('hello')
    print t.c('hello')
    print t.c('h')
    print t.c('hello')
    print cc('he')
    print cc('he')