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Python 注解方式实现缓存数据详解

2022-02-11 23:06liuxing93619 Python

这篇文章主要介绍了Python 注解方式实现缓存数,文中通过示例代码介绍的非常详细,对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下

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

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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
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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

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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

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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

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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

总结

本篇文章就到这里了,希望能够给你带来帮助,也希望您能够多多关注服务器之家的更多内容!

原文链接:https://blog.csdn.net/liuxing93619/article/details/120837018

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