No more 429: Combining ratelimit and requests_cache

requests_cache is nice. ratelimit is nice. But they don’t play nicely together yet: If a request is coming from the cache that requests_cache maintains, ratelimit doesn’t “know that” and will still slow your script down for no reason. That’s why I published the ratelimit_requests_cache module. It offers a similar rate limiter to the ratelimit module, but invocations only count towards the rate limit if the request could not be served from the cache.

The usage is the same as the normal ratelimit package. You decorate a method with the sleep_and_retry and a limiting decorator, in this case the limits_if_not_cached:

import requests
import requests_cache
from ratelimit import sleep_and_retry
from ratelimit_requests_cache import limits_if_not_cached


@sleep_and_retry
@limits_if_not_cached(calls=1, period=1)
def get_from_httpbin(i):
    return requests.get(f'https://httpbin.org/anything?i={i}')


# Enable requests caching
requests_cache.install_cache()

# Notice that only the first ten requests will be ratelimited to 1 request / second
# After that, it's a lot quicker since requests can be served from the cache
# and the ratelimiter does not engage
for i in range(100):
    get_from_httpbin(i % 10)
    print(i)

See it in action:

This rate limiter is ideal for when an API call is expensive, measured in either time or in money. HTTP requests have to be performed only once, and you can better avoid getting HTTP 429 status codes.

This rate limiter checks whether a request was served from the cache or not by checking the .from_cache attribute of the Response. That means that if you have a different caching mechanism, you could also set this .from_cache boolean attribute and use the decorator for other purposes just as easily.

To start using it, get it from PyPI:

python3 -m pip install ratelimit_requests_cache