Using @functools.lru_cache with dictionary arguments

Question

I have a method that takes (among others) a dictionary as an argument. The method is parsing strings and the dictionary provides replacements for some substrings, so it does

Answer 1

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():
    ...