04--定义item,使用meta在不同解析函数之间传递参数

使用爬阳光政务平台的例子

创建项目

scrapy startproject yg

scrapy genspider yguang wz.sun0769.com

文件结构

定义item

到item.py中
只有在item.py中定义的字段才能在yg.py中使用

# -*- coding: utf-8 -*-

# Define here the models for your scraped items
#
# See documentation in:
# https://doc.scrapy.org/en/latest/topics/items.html

import scrapy


class SunshineItem(scrapy.Item):
    # define the fields for your item here like:
    # name = scrapy.Field()
    title = scrapy.Field()
    href = scrapy.Field()
    publish_date = scrapy.Field()
    content_img = scrapy.Field()
    content = scrapy.Field()

yg.py

注意定义meta的方式,在不同的parse之间传递item需要定义meta

# -*- coding: utf-8 -*-
import scrapy
from sunshine.items import SunshineItem

class YgSpider(scrapy.Spider):
    name = 'yg'
    allowed_domains = ['sun0769.com']
    start_urls = ['http://wz.sun0769.com/index.php/question/questionType?type=4&page=0']

    def parse(self, response):# 处理列表页
        # 分组
        tr_list = response.xpath("//div[@class='greyframe']/table[2]/tr/td/table/tr")
        for tr in tr_list:
            item = SunshineItem()
            item['title'] = tr.xpath("./td[2]/a[2]/@title").extract_first()
            item['href'] = tr.xpath("./td[2]/a[2]/@href").extract_first()
            item['publish_date'] = tr.xpath("./td[last()]/text()").extract_first()

            # 到详情页里面去
            yield scrapy.Request(
                item['href'],
                callback = self.parse_detail,
                meta={"item":item} # 提取的数据不完全,给到callback函数继续处理
            )
        # 翻页
        next = response.xpath("//a[text()]='>'/@href").extract_first()
        if next is not None:
            yield scrapy.Request(
                next,
                callback=self.parse
            )

    def parse_detail(self,response): # 处理详情页
        item = response.meta['item']
        # extract()提取列表,extract_first()提取第一个
        item['content'] = response.xpath("//td[@class='txt16_3']//text()").extract()
        item['content_img'] = response.xpath("//td[@class='txt16_3']//img/@src").extract()
        item['content_img'] = ["http://wz.sun0769.com"+i for i  in item['content_img']]
        # print(item)
        yield item

处理数据

因为爬到的数据content中有一些我们不需要的字段,我们需要删除
到管道piplines.py中

# -*- coding: utf-8 -*-

# Define your item pipelines here
#
# Don't forget to add your pipeline to the ITEM_PIPELINES setting
# See: https://doc.scrapy.org/en/latest/topics/item-pipeline.html
import re

class SunshinePipeline(object):
    def process_item(self, item, spider):
        item['content'] = self.process_codntent(item['content'])
        print(item)
        return item

    def process_codntent(self,content):
        content = [re.sub("\xa0|\s","",i)for i in content]
        content = [i for i in content if len(i)>0] # 去除列表中空字符串
        return content

第一个私有函数调用第二个处理字符串的私有函数

注意

使用管道的时候需要在setting中把管道解开

定义log_level,以及把user_agent改成自己的