scrapy两层爬取链接问题：Request url must be str or unicode

要抓多个页面，用for循环把每一页的地址写出来，但是有错误：
错误代码：（ps：爬取的网页编码是gbk）

raise TypeError('Request url must be str or unicode, got %s:' % type(url).__name__)
TypeError: Request url must be str or unicode, got list:

爬虫代码如下：

#-*-coding:utf8-*-
import scrapy
from scrapy_redis.spiders import RedisSpider
from scrapy.http import Request
from scrapy.selector import Selector
from Articlespider.items import ArticlespiderItem
import re



class Articlespider(RedisSpider):
    name = "article"
    redis_key = 'article:start_urls'
    allowed_domains=["yyyy.com"]
    start_urls = ['http://www.yyyy.com/articles/articles-list.php'
                  ]
    #生成要抓取的url地址，从1-100页，每一页都是文章列表页
    def start_requests(self):
        pages=[]
        for i in range(1,100):
            newpage=scrapy.Request("http://www.yyyy.com/articles/articles-list.php?pagenum=%s"%i)
            pages.append(newpage)
        return pages

    #在文章列表页获取文章详情页的url
    def parse(self, response):
        selector = Selector(response)
        articles=selector.xpath('//div[@class="articlename"]')
        for eacharticle in articles:
            articleUrl=eacharticle.xpath('a/@href').extract()
            yield Request(articleUrl,callback=self.parse_articleInfo)

    #接收到文章详情页的url，抓取文章详情
    def parse_articleInfo(self,response):
        selector = Selector(response)
        item=ArticlespiderItem()
        item['articlename']=selector.xpath('/html/body/div[4]/div[2]/div[1]/div[1]/h3/text()').extract()
        item['content']=selector.xpath('/html/body/div[5]/div[2]/div[1]/div[3]/p/text()').extract()
        yield item

---

articleUrl=eacharticle.xpath('a/@href').extract()[0]