使用缓存在Python上创建Memoize装饰器

Question

我正在使用 Datacamp 课程来学习装饰器，我承认我对缓存主题还很陌生。

让我陷入困境的是，我在他们的课程中遵循“示例”记忆装饰器，它在 jupyter 笔记本上抛出错误，尽管它与他们的课程完全相同：

def memoize(func):
    '''Store the results of the decorated function for fast look up'''
    #Store results in a dict that maps arguments to results
    cache = {}
    #As usual, create the wrapper to create the newly decorated function
    def wrapper(*args, **kwargs):
        # If these arguments havent been seen before...
        if (args, kwargs) not in cache:
            #Call func() and store the result.
            cache[(args, kwargs)] =func(*args, **kwargs)
        #Now we can look them up quickly
        return cache[(args, kwargs)]
    
    return wrapper 

我使用具有以下功能的装饰器：

@memoize
def slow_function(a,b):
    print('Sleeping...')
    time.sleep(5)
    return a+b

错误是unhashable类型的dict。如果有人能解释这个错误的原因，我将非常感激。

提前致谢。

Answer 1

试试这个：

import time

def memoize(func):
    """
    Store the results of the decorated function for fast lookup
    """
    # store results in a dict that maps arguments to results
    cache = {}
    # define the wrapper function to return
    def wrapper(*args, **kwargs):
        # if these arguments haven't been seen before
        if (str(args), str(kwargs)) not in cache:
            # call func() and store the result
            cache[(str(args), str(kwargs))] = func(*args, **kwargs)
        return cache[(str(args), str(kwargs))]
    return wrapper


@memoize
def slow_function(a, b):
    print('Sleeping...')
    time.sleep(5)
    return a + b

Answer 2

Python 中的字典对其键有一些先决条件，请参阅：https://wiki.python.org/moin/DictionaryKeys

解决方案是将参数从各种类型转换为可哈希类型，例如字符串。