Python LRU Cache Decorator Per Instance

Question

Using the LRU Cache decorator found here: http://code.activestate.com/recipes/578078-py26-and-py30-backport-of-python-33s-lru-cache/

from lru_cache import lr         


        

Answer 1

How about this: a function decorator that wraps the method with lru_cache the first time it's called on each instance?

def instance_method_lru_cache(*cache_args, **cache_kwargs):
    def cache_decorator(func):
        @wraps(func)
        def cache_factory(self, *args, **kwargs):
            print('creating cache')
            instance_cache = lru_cache(*cache_args, **cache_kwargs)(func)
            instance_cache = instance_cache.__get__(self, self.__class__)
            setattr(self, func.__name__, instance_cache)
            return instance_cache(*args, **kwargs)
        return cache_factory
    return cache_decorator

Use it like this:

class Foo:
    @instance_method_lru_cache()
    def times_2(self, bar):
        return bar * 2

foo1 = Foo()
foo2 = Foo()

print(foo1.times_2(2))
# creating cache
# 4
foo1.times_2(2)
# 4

print(foo2.times_2(2))
# creating cache
# 4
foo2.times_2(2)
# 4

Here's a gist on GitHub with some inline documentation.