考虑以下几点:

@property
def name(self):

    if not hasattr(self, '_name'):

        # expensive calculation
        self._name = 1 + 1

    return self._name

我是新来的,但我认为缓存可以分解成一个装饰器。只是我没有找到一个这样的;)

PS,真正的计算不依赖于可变值


当前回答

我实现了类似的东西,使用pickle进行持久化,使用sha1进行简短的几乎唯一的id。基本上,缓存对函数代码和参数的历史进行哈希,以获得sha1,然后查找名称为sha1的文件。如果它存在,则打开它并返回结果;如果没有,则调用该函数并保存结果(如果需要一定时间来处理,则可以选择只保存结果)。

也就是说,我发誓我找到了一个现有的模块,它做到了这一点,并发现自己在这里试图找到该模块……我能找到的最接近的是这个,看起来差不多:http://chase-seibert.github.io/blog/2011/11/23/pythondjango-disk-based-caching-decorator.html

我看到的唯一问题是,它不能很好地用于大输入,因为它散列str(arg),这不是唯一的大型数组。

如果有一个unique_hash()协议,让一个类返回其内容的安全散列,那就太好了。我基本上是手动实现我所关心的类型。

其他回答

@lru_cache不适合默认attrs

我的@mem装饰:

import inspect
from copy import deepcopy
from functools import lru_cache, wraps
from typing import Any, Callable, Dict, Iterable


# helper
def get_all_kwargs_values(f: Callable, kwargs: Dict[str, Any]) -> Iterable[Any]:
    default_kwargs = {
        k: v.default
        for k, v in inspect.signature(f).parameters.items()
        if v.default is not inspect.Parameter.empty
    }

    all_kwargs = deepcopy(default_kwargs)
    all_kwargs.update(kwargs)

    for key in sorted(all_kwargs.keys()):
        yield all_kwargs[key]


# the best decorator
def mem(func: Callable) -> Callable:
    cache = dict()

    @wraps(func)
    def wrapper(*args, **kwargs) -> Any:
        all_kwargs_values = get_all_kwargs_values(func, kwargs)
        params = (*args, *all_kwargs_values)
        _hash = hash(params)

        if _hash not in cache:
            cache[_hash] = func(*args, **kwargs)

        return cache[_hash]

    return wrapper


# some logic
def counter(*args) -> int:
    print(f'* not_cached:', end='\t')
    return sum(args)


@mem
def check_mem(a, *args, z=10) -> int:
    return counter(a, *args, z)


@lru_cache
def check_lru(a, *args, z=10) -> int:
    return counter(a, *args, z)


def test(func) -> None:
    print(f'\nTest {func.__name__}:')

    print('*', func(1, 2, 3, 4, 5))
    print('*', func(1, 2, 3, 4, 5))
    print('*', func(1, 2, 3, 4, 5, z=6))
    print('*', func(1, 2, 3, 4, 5, z=6))
    print('*', func(1))
    print('*', func(1, z=10))


def main():
    test(check_mem)
    test(check_lru)


if __name__ == '__main__':
    main()

输出:

Test check_mem:
* not_cached:   * 25
* 25
* not_cached:   * 21
* 21
* not_cached:   * 11
* 11

Test check_lru:
* not_cached:   * 25
* 25
* not_cached:   * 21
* 21
* not_cached:   * 11
* not_cached:   * 11
from functools import wraps


def cache(maxsize=128):
    cache = {}

    def decorator(func):
        @wraps(func)
        def inner(*args, no_cache=False, **kwargs):
            if no_cache:
                return func(*args, **kwargs)

            key_base = "_".join(str(x) for x in args)
            key_end = "_".join(f"{k}:{v}" for k, v in kwargs.items())
            key = f"{key_base}-{key_end}"

            if key in cache:
                return cache[key]

            res = func(*args, **kwargs)

            if len(cache) > maxsize:
                del cache[list(cache.keys())[0]]
                cache[key] = res

            return res

        return inner

    return decorator


def async_cache(maxsize=128):
    cache = {}

    def decorator(func):
        @wraps(func)
        async def inner(*args, no_cache=False, **kwargs):
            if no_cache:
                return await func(*args, **kwargs)

            key_base = "_".join(str(x) for x in args)
            key_end = "_".join(f"{k}:{v}" for k, v in kwargs.items())
            key = f"{key_base}-{key_end}"

            if key in cache:
                return cache[key]

            res = await func(*args, **kwargs)

            if len(cache) > maxsize:
                del cache[list(cache.keys())[0]]
                cache[key] = res

            return res

        return inner

    return decorator

示例使用

import asyncio
import aiohttp


# Removes the aiohttp ClientSession instance warning.
class HTTPSession(aiohttp.ClientSession):
    """ Abstract class for aiohttp. """
    
    def __init__(self, loop=None) -> None:
        super().__init__(loop=loop or asyncio.get_event_loop())

    def __del__(self) -> None:
        if not self.closed:
            self.loop.run_until_complete(self.close())
            self.loop.close()
 

        return 
       

            

session = HTTPSession()

@async_cache()
async def query(url, method="get", res_method="text", *args, **kwargs):
    async with getattr(session, method.lower())(url, *args, **kwargs) as res:
        return await getattr(res, res_method)()


async def get(url, *args, **kwargs):
    return await query(url, "get", *args, **kwargs)
 

async def post(url, *args, **kwargs):
    return await query(url, "post", *args, **kwargs)

async def delete(url, *args, **kwargs):
    return await query(url, "delete", *args, **kwargs)

从Python 3.2开始,有一个内置的装饰器:

@functools。lru_cache(最大容量= 100,输入= False)

装饰器使用一个可记忆可调用对象来包装函数,该可调用对象最多保存maxsize最近的调用。当使用相同的参数周期性地调用昂贵的或I/O绑定的函数时,它可以节省时间。

用于计算斐波那契数的LRU缓存示例:

from functools import lru_cache

@lru_cache(maxsize=None)
def fib(n):
    if n < 2:
        return n
    return fib(n-1) + fib(n-2)

>>> print([fib(n) for n in range(16)])
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610]

>>> print(fib.cache_info())
CacheInfo(hits=28, misses=16, maxsize=None, currsize=16)

如果你被Python 2困住了。X,这里是其他兼容的内存库列表:

functools32 | PyPI |源代码 repoze。lru | PyPI |源代码 pylru | PyPI |源代码 补丁。functools_lru_cache | PyPI |源代码

class memorize(dict):
    def __init__(self, func):
        self.func = func

    def __call__(self, *args):
        return self[args]

    def __missing__(self, key):
        result = self[key] = self.func(*key)
        return result

示例使用:

>>> @memorize
... def foo(a, b):
...     return a * b
>>> foo(2, 4)
8
>>> foo
{(2, 4): 8}
>>> foo('hi', 3)
'hihihi'
>>> foo
{(2, 4): 8, ('hi', 3): 'hihihi'}

Werkzeug有一个cached_property装饰器(docs, source)