Get proxy ip address scrapy using to crawl

I use Tor to crawl web pages. I started tor and polipo service and added

class ProxyMiddleware(object):   # overwrite process request   def
  process_request(self, request, spider):
     # Set the location of the proxy
    request.meta['proxy'] = "127.0.0.1:8123"

Now, how can I make sure that scrapy uses different IP address for requests?

You can yield the first request to check your public IP, and compare this to the IP you see when you go to http://checkip.dyndns.org/ without using Tor/VPN. If they are not the same, scrapy is using a different IP obviously.

def start_requests(self):
    yield Request('http://checkip.dyndns.org/', callback=self.check_ip)
    # yield other requests from start_urls here if needed

def check_ip(self, response):
    pub_ip = response.xpath('//body/text()').re('\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}')[0]
    print "My public IP is: " + pub_ip
   
    # yield other requests here if needed