这个豆瓣爬虫的案例，“下一页”的实现是抓取的(倒数第6行)，如果改为for循环怎么写呢？

 # -*- coding: utf-8 -*-
import scrapy
from scrapy.contrib.spiders import CrawlSpider
from scrapy.http import Request
from scrapy.selector import Selector
from doubanmovie.items import DoubanmovieItem

class Douban(CrawlSpider):
name = "douban"
redis_key = 'douban:start_urls'
start_urls = ['http://movie.douban.com/top250']

url = 'http://movie.douban.com/top250'

def parse(self,response):
    # print response.body
    item = DoubanmovieItem()
    selector = Selector(response)
    Movies = selector.xpath('//div[@class="info"]')
    for eachMoive in Movies:
        title = eachMoive.xpath('div[@class="hd"]/a/span/text()').extract()
        fullTitle = ''
        for each in title:
            fullTitle += each
        movieInfo = eachMoive.xpath('div[@class="bd"]/p/text()').extract()
        star = eachMoive.xpath('div[@class="bd"]/div[@class="star"]/span/em/text()').extract()[0]
        quote = eachMoive.xpath('div[@class="bd"]/p[@class="quote"]/span/text()').extract()
        #quote可能为空，因此需要先进行判断
        if quote:
            quote = quote[0]
        else:
            quote = ''
        item['title'] = fullTitle
        item['movieInfo'] = ';'.join(movieInfo)
        item['star'] = star
        item['quote'] = quote
        yield item
    nextLink = selector.xpath('//span[@class="next"]/link/@href').extract()
    #第10页是最后一页，没有下一页的链接
    if nextLink:
        nextLink = nextLink[0]
        print nextLink
        yield Request(self.url + nextLink,callback=self.parse)