Python2的function cache实现

今天看到Python3中有lru_cache的function cache，无聊就试着在Python2.7中实现了一个简单的版本：

#!env python
#coding=utf-8
# 
# Author:       [email protected]
# 
# Created Time: 2017年05月28日 星期日 09时34分06秒
# 
# FileName:     test_decorator_cache.py
# 
# Description:  
# 
# ChangeLog:

from functools import wraps
from collections import OrderedDict

def cache(maxsize = 10):
    def cache_decorator(fn):
        _cache = OrderedDict()
        @wraps(fn)
        def inner(*args, **kwargs):
            if args in _cache:
                print 'hit cache!'
                return _cache.get(args)
            r = fn(*args, **kwargs)
            if len(_cache) >= maxsize:
                _key = _cache.keys()[0]
                del _cache[_key]
                print 'queue is full, del _cache[%s]' % (_key)
            return _cache.setdefault(args, r)

        return inner
    return cache_decorator

@cache(maxsize = 2)
def fn(i):
    print 'get fn(%d).' % (i)
    return i*i

print fn(11)
print fn(13)
print fn(11)
print fn(15)
print fn(11)
print fn(13)

输出如下：

get fn(11).
121
get fn(13).
169
hit cache!
121
get fn(15).
queue is full, del _cache[11]
225
get fn(11).
queue is full, del _cache[13]
121
get fn(13).
queue is full, del _cache[15]
169