Python in-memory cache with time to live

Question

I have multiple threads running the same process that need to be able to to notify each other that something should not be worked on for the next n seconds its not the end o

Answer 1

I absolutely love the idea from @iutinvg, I just wanted to take it a little further. Decouple it from having to know to pass the ttl and just make it a decorator so you don't have to think about it. If you have django, py3 and don't feel like pip installing any dependencies, try this out.

import time
from django.utils.functional import lazy
from functools import lru_cache, partial, update_wrapper


def lru_cache_time(seconds, maxsize=None):
    """
    Adds time aware caching to lru_cache
    """
    def wrapper(func):
        # Lazy function that makes sure the lru_cache() invalidate after X secs
        ttl_hash = lazy(lambda: round(time.time() / seconds), int)()
        
        @lru_cache(maxsize)
        def time_aware(__ttl, *args, **kwargs):
            """
            Main wrapper, note that the first argument ttl is not passed down. 
            This is because no function should bother to know this that 
            this is here.
            """
            def wrapping(*args, **kwargs):
                return func(*args, **kwargs)
            return wrapping(*args, **kwargs)
        return update_wrapper(partial(time_aware, ttl_hash), func)
    return wrapper


@lru_cache_time(seconds=10)
def meaning_of_life():
    """
    This message should show up if you call help().
    """
    print('this better only show up once!')
    return 42


@lru_cache_time(seconds=10)
def multiply(a, b):
    """
    This message should show up if you call help().
    """
    print('this better only show up once!')
    return a * b
    
# This is a test, prints a `.` for every second, there should be 10s 
# between each "this better only show up once!" *2 because of the two functions.
for _ in range(20):
    meaning_of_life()
    multiply(50, 99991)
    print('.')
    time.sleep(1)