scrapy中对于item的把控

其实很简单，就是想要存储的位置发生改变。直接看例子，然后触类旁通。

以大众点评 评论的内容为例 ，位置:http://www.dianping.com/shop/77489519/review_more?pageno=1

数据存储形式由A 变成B

A:

展开的话这样子:

B:

本质上看，就是多个相同类型的item可以合并，不需要那么多，分别来看下各自的代码:

A:

class GengduopinglunSpider(scrapy.Spider):
    name = ‘gengduopinglun‘
    start_urls = [‘http://www.dianping.com/shop/77489519/review_more?pageno=1‘]

    def parse(self, response):
        item=PinglunItem()
        comment = item[‘comment‘] if "comment" in item else []
        for i in response.xpath(‘//div[@class="content"]‘):
            for j in i.xpath(‘.//div[@class="J_brief-cont"]/text()‘).extract():
                comment.append(j.strip())
        item[‘comment‘]=comment
        next_page = response.xpath(
            ‘//div[@class="Pages"]/div[@class="Pages"]/a[@class="NextPage"]/@href‘).extract_first()
        item[‘_id‘]=next_page
        # item[‘_id‘]=‘onlyone‘
        if next_page != None:
            next_page = response.urljoin(next_page)
            # yield Request(next_page, callback=self.shop_comment,meta={‘item‘: item})
            yield Request(next_page, callback=self.parse,)
        yield item

B:

class GengduopinglunSpider(scrapy.Spider):
    name = ‘gengduopinglun‘
    start_urls = [‘http://www.dianping.com/shop/77489519/review_more?pageno=1‘]

    def parse(self, response):
        item=PinglunItem()
        comment = item[‘comment‘] if "comment" in item else []
        for i in response.xpath(‘//div[@class="content"]‘):
            for j in i.xpath(‘.//div[@class="J_brief-cont"]/text()‘).extract():
                comment.append(j.strip())
        item[‘comment‘]=comment
        next_page = response.xpath(
            ‘//div[@class="Pages"]/div[@class="Pages"]/a[@class="NextPage"]/@href‘).extract_first()
        # item[‘_id‘]=next_page
        item[‘_id‘]=‘onlyone‘
        if next_page != None:
            next_page = response.urljoin(next_page)
            yield Request(next_page, callback=self.shop_comment,meta={‘item‘: item})
            # yield Request(next_page, callback=self.parse,)
        # yield item

    def shop_comment(self, response):
        item = response.meta[‘item‘]
        comment = item[‘comment‘] if "comment" in item else []
        for i in response.xpath(‘//div[@class="content"]‘):
            for j in i.xpath(‘.//div[@class="J_brief-cont"]/text()‘).extract():
                comment.append(j.strip())
        item[‘comment‘]=comment
        next_page = response.xpath(
            ‘//div[@class="Pages"]/div[@class="Pages"]/a[@class="NextPage"]/@href‘).extract_first()
        if next_page != None:
            next_page = response.urljoin(next_page)
            yield Request(next_page, callback=self.shop_comment,meta={‘item‘: item})
        yield item

B里面是有重复代码的，这个无关紧要，只是演示，注意看两个yield 的区别

以上只是演示scrapy中yield的用法，用来控制item，其余pipline，setting未展示.