如何根据单个scrapy.Spider的不同命令设置不同的IP？

IP_POOL = [
    'http://ip1:port',
    'http://ip2:port',
    'http://ip3:port',
    ...
]

from scrapy import signals
import random

class IPProxyMiddleware(object):
    def __init__(self, ip_pool):
        self.ip_pool = ip_pool

    @classmethod
    def from_crawler(cls, crawler):
        ip_pool = crawler.settings.get('IP_POOL')
        return cls(ip_pool)

    def process_request(self, request, spider):
        ip_proxy = random.choice(self.ip_pool)
        request.meta['proxy'] = ip_proxy

DOWNLOADER_MIDDLEWARES = {
    'your_project_name.middlewares.IPProxyMiddleware': 543,
}

class MySpider(scrapy.Spider):
    name = 'my_spider'
    ...

    def __init__(self, proxy=None, *args, **kwargs):
        super(MySpider, self).__init__(*args, **kwargs)
        self.proxy = proxy

    def start_requests(self):
        if self.proxy:
            # 使用Spider指定的IP代理
            request = scrapy.Request(url=self.start_urls[0], callback=self.parse, meta={'proxy': self.proxy})
        else:
            # 使用全局IP代理池
            request = scrapy.Request(url=self.start_urls[0], callback=self.parse)
        yield request