#!usr/bin/env python
# -*- coding:utf-8 -*-

from functools import wraps

def memo(fn):
    """
    调用函数前查询一下缓存,
    如果没有才调用,有就从缓存中返回值
    """
    cache = {}
    miss = object()

    @wraps(fn)
    def wrapper(*args):
        result = cache.get(args, miss)
        if result is miss:
            result = fn(*args)
            cache[args] = result
        return result
    return wrapper

@memo
def fib(n):
    if n < 2:
        return n
    return fib(n - 1) + fib(n - 2)


if __name__ == "__main__":
    print(fib(12))