Configure lru_cache for class and static methods

Question

I am trying to use lru_cache in Python3 to speed up common queries into our Salesforce database. Below is the relevant code that is supposed to

• a) convert non-hashable arguments to hashable ones, and
• b) enable the LRU cache for those objects.

When I try this code, the cache works for calling the functions with no arguments, but it doesn't seem to cache the function calls with arguments. Also, I am not sure of how to order the decorators for the decorated functions.

Note, I am using a class here with class and static methods so I can override the get and get_all methods for different subclasses of Resource.

Please explain what I am doing wrong or could be doing better.

from functools import lru_cache
from functools import wraps

class Resource(object):

    def hash_dict(func):
        """Transform mutable dictionnary
           Into immutable
           Useful to be compatible with cache
        """
        class HDict(dict):
            def __hash__(self):
                return hash(frozenset(self.items()))

        @wraps(func)
        def wrapped(*args, **kwargs):
            args = tuple([HDict(arg) if isinstance(arg, dict) else arg for arg in args])
            kwargs = {}
            for k, v in kwargs.items():
                if isinstance(v, dict):
                    kwargs[k] = HDict(v)
                elif isinstance(v, list):
                    kwargs[k] = tuple(v)
                else:
                    kwargs[k] = v
            return func(*args, **kwargs)
        return wrapped

    @staticmethod
    @hash_dict
    @lru_cache
    def get(cls, resource_id, lang='en', fields=None):
        pass

    @classmethod
    @hash_dict
    @lru_cache
    def get_all(cls, lang='en', filters=None, fields=None):
        pass

Answer 1

No need for an additional package. The following work as expected:

import functools


class A:

  @staticmethod
  @functools.lru_cache(maxsize=None)
  def build(value):
    print('Creating', value)
    return A()


assert A.build('a') is A.build('a')
assert A.build('b') is A.build('b')
assert A.build('b') is not A.build('a')

Starting python 3.9, you can replace @functools.lru_cache(maxsize=None) by @functools.cache.