实现一个cache装饰器 实现可过期被清除的功能

from functools import wraps
import inspect
import time
import datetime

def m_cache(fn):
    local_cache = {}
    def wrapper(*args, **kwargs):
        # local_cache有没有过期的key
        expire_keys = []
        for k,(_,ts) in local_cache.items():
            if datetime.datetime.now().timestamp()- ts >5 :
                expire_keys.append(k)
        for k in expire_keys:
            local_cache.pop(k)


        key_dict = {} #sorted
        sig = inspect.signature(fn)
        params = sig.parameters #有序字典

        param_list = list(params.keys())
        # 位置参数
        for i,v in enumerate(args):

            k = param_list[i]
            key_dict[k] = v
        # 关键字
        # for k,v in kwargs.items():
        #     key_dict[k] = v
        key_dict.update(kwargs)

        # 缺省值
        for k in params.keys():
            if k not in key_dict.keys():
                key_dict[k] = params[k].default

        key = tuple(sorted(key_dict.items()))
        if key not in local_cache.keys():
            ret = fn(*args, **kwargs)
            local_cache[key] = (ret,datetime.datetime.now().timestamp())
        return local_cache[key ]
    return wrapper

@m_cache
def add(x,y=5):
    time.sleep(3)
    ret = x+y
    return ret


if __name__ == "__main__":
    print(add(4))
    print(add(4,5))
    print(add(4,y=5))
    print(add(y=5,x=4))