Python 注解方式实现缓存数据详解

2024-04-02 19:04:59 253人浏览安东尼

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摘要

目录背景拿来即用实践过程通过装饰器类简化代码总结背景每次加载数据都要重新Load，想通过加入的注解方式开发缓存机制，每次缓存不用写代码了缺点：目前仅支持一个返回值，虽然能弄成字

背景

每次加载数据都要重新Load，想通过加入的注解方式开发缓存机制，每次缓存不用写代码了

缺点：目前仅支持一个返回值，虽然能弄成字典，但是已经满足个人需求，没动力改(狗头)。

拿来即用

新建文件 Cache.py


class Cache:
    def __init__(self, cache_path='.', nocache=False):
        self.cache_path = cache_path
        self.cache = not nocache
    def __call__(self, func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            s = f'{func.__code__.co_filename}.{func.__name__}'
            s += ','.join(list(args[1:]) + [f'{k}={v}' for k, v in kwargs.items()])
            md5 = hashlib.md5()
            md5.update(s.encode('utf-8'))
            cache_file = f'{self.cache_path}/{md5.hexdigest()}'
            if self.cache and os.path.exists(cache_file):
                print('Loading from cache')
                return pickle.load(open(cache_file, 'rb'))
            else:
                if not os.path.exists(self.cache_path):
                    os.makedirs(self.cache_path)
                data = func(*args, **kwargs)
                pickle.dump(data, file=open(cache_file, 'wb'))
                print(f'Dump finished {cache_file}')
            return data
        return wrapper


from .Cache import Cache
@Cache(root_path, nocache=True)
def load_data(self, inpath):
    return 'Wula~a~a~!'

实践过程

第一次，来个简单的继承父类


class Cache(object):
    def __init__(self, cache_path=None):
        self.cache_path = cache_path if cache_path else '.'
        self.cache_path = f'{self.cache_path}/cache'
        self.data = self.load_cache()
    def load_cache(self):
        if os.path.exists(self.cache_path):
            print('Loading from cache')
            return pickle.load(open(self.cache_path, 'rb'))
        else:
            return None
    def save_cache(self):
        pickle.dump(self.data, file=open(self.cache_path, 'wb'))
        print(f'Dump finished {self.cache_path}')
class Filter4Analyzer(Cache):
    def __init__(self, rootpath, datapath):
        super().__init__(rootpath)
        self.root_path = rootpath
        if self.data is None:
            self.data = self.load_data(datapath)
            self.save_cache()

只要继承Cache类就可以啦，但是有很多局限，例如只能指定某个参数被cache，例如还得在Filter4Analyzer里面写保存的代码。

下一步，python嵌套装饰器来改善这个问题


from functools import wraps
import hashlib
def cached(cache_path):
    def wrapperper(func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            s = f'{func.__code__.co_filename}.{func.__name__}' + ','.join(args[1:])
            s += ','.join(list(args[1:]) + [f'{k}={v}' for k, v in kwargs.items()])
            md5 = hashlib.md5()
            md5.update(s.encode('utf-8'))
            cache_file = f'{cache_path}/{md5.hexdigest()}' if cache_path else './cache'
            if os.path.exists(cache_file):
                print('Loading from cache')
                return pickle.load(open(cache_file, 'rb'))
            else:
                if not os.path.exists(cache_path):
                    os.makedirs(cache_path)
                data = func(*args, **kwargs)
                pickle.dump(data, file=open(cache_file, 'wb'))
                print(f'Dump finished {cache_file}')
            return data
        return wrapper
    return wrapperper
class Tester:
    @cached(cache_path='./workpath_test')
    def test(self, data_path):
        return ['hiahia']

通过装饰器类简化代码


class Cache:
    def __init__(self, cache_path='.', nocache=False):
        self.cache_path = cache_path
        self.cache = not nocache
    def __call__(self, func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            s = f'{func.__code__.co_filename}.{func.__name__}'
            s += ','.join(list(args[1:]) + [f'{k}={v}' for k, v in kwargs.items()])
            md5 = hashlib.md5()
            md5.update(s.encode('utf-8'))
            cache_file = f'{self.cache_path}/{md5.hexdigest()}'
            if self.cache and os.path.exists(cache_file):
                print('Loading from cache')
                return pickle.load(open(cache_file, 'rb'))
            else:
                if not os.path.exists(self.cache_path):
                    os.makedirs(self.cache_path)
                data = func(*args, **kwargs)
                pickle.dump(data, file=open(cache_file, 'wb'))
                print(f'Dump finished {cache_file}')
            return data
        return wrapper

参考：

Python 函数装饰器

Python函数属性和PyCodeObject