Python自定义翻页老出现问题

学习爬京东众筹前50页热卖商品信息，可以翻页，但不按顺序翻页，乱跳，请问是哪里出现问题了呢

import scrapy
# 导入items类， 使items类生效
from jd1.items import Jd1Item
import time

class Jdzch1Spider(scrapy.Spider):
    name = 'jdzch1'
    start_urls = ['https://z.jd.com/bigger/search.html?sort=zhtj&page=1']

    def parse(self, response):
            result = response.xpath('//li[@class="info type_now"]')
        # 循环每个商品，提取所需信息
            for i in result:
            # 定义 item 字典
                item = Jd1Item()
                # 筛选信息
                item['title'] = i.xpath('.//h4[@class="link-tit"]/text()').extract_first()
                item['perc'] = i.xpath('.//li[@class="fore1"]/p[@class="p-percent"]/text()').extract_first()
                item['outc1'] = i.xpath('.//li[@class="fore1"]/p[@class="p-extra"]/text()').extract_first()
                item['money'] = i.xpath('.//li[@class="fore2"]/p[@class="p-percent"]/text()').extract_first()
                item['outc2'] = i.xpath('.//li[@class="fore2"]/p[@class="p-extra"]/text()').extract_first()
                item['time'] = i.xpath('.//li[@class="fore3"]/p[@class="p-percent"]/text()').extract_first()
                item['outc3'] = i.xpath('.//li[@class="fore3"]/p[@class="p-extra"]/text()').extract_first()
                yield item
            time.sleep(3)

    def start_requests(self):
        j = 1
        for j in range(5,0)[::-1]:       
            newurl = "https://z.jd.com/bigger/search.html?sort=zhtj&page=%d"  %  (j)
            yield scrapy.Request(newurl, callback=self.parse)

改下试试

 def start_requests(self):
        for j in range(1,51):       
            newurl = "https://z.jd.com/bigger/search.html?sort=zhtj&page=%d"  %  (j)
            yield scrapy.Request(newurl, callback=self.parse)