Using @functools.lru_cache with dictionary arguments

Instead of using a custom hashable dictionary, use this and avoid reinventing the wheel! It's a frozen dictionary that's all hashable.

https://pypi.org/project/frozendict/

Code:

from frozendict import frozendict

def freezeargs(func):
    """Transform mutable dictionnary
    Into immutable
    Useful to be compatible with cache
    """

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

and then

@freezeargs
@lru_cache
def func(...):
    pass

Code taken from @fast_cen 's answer

Note: this does not work on recursive datastructures; for example, you might have an argument that's a list, which is unhashable. You are invited to make the wrapping recursive, such that it goes deep into the data structure and makes every dict frozen and every list tuple.

(I know that OP nolonger wants a solution, but I came here looking for the same solution, so leaving this for future generations)

What about creating a hashable dict class like so:

class HDict(dict):
    def __hash__(self):
        return hash(frozenset(self.items()))

substs = HDict({'foo': 'bar', 'baz': 'quz'})
cache = {substs: True}

How about subclassing namedtuple and add access by x["key"]?

class X(namedtuple("Y", "a b c")):
    def __getitem__(self, item):
        if isinstance(item, int):
            return super(X, self).__getitem__(item)
        return getattr(self, item)

Here is a decorator that use @mhyfritz trick.

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()))

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

Simply add it before your lru_cache.

@hash_dict
@functools.lru_cache()
def your_function():
    ...