Middleware de proxy no Scrapy

import itertools, random

class RotatingProxyMiddleware:
    def __init__(self):
        with open("proxies.txt") as handle:
            self.proxies = [line.strip() for line in handle if line.strip()]
        random.shuffle(self.proxies)
        self.pool = itertools.cycle(self.proxies)

    def process_request(self, request, spider):
        request.meta["proxy"] = f"http://{next(self.pool)}"

DOWNLOADER_MIDDLEWARES = {
    "myproject.middlewares.RotatingProxyMiddleware": 350,
    "scrapy.downloadermiddlewares.retry.RetryMiddleware": 550,
}
RETRY_TIMES = 5
DOWNLOAD_TIMEOUT = 10