python爬虫库scrapy简单使用实例详解

最近因为项目需求，需要写个爬虫爬取一些题库。在这之前爬虫我都是用node或者php写的。一直听说python写爬虫有一手，便入手了python的爬虫框架scrapy.

下面简单的介绍一下scrapy的目录结构与使用：

首先我们得安装scrapy框架

pip install scrapy

接着使用scrapy命令创建一个爬虫项目：

scrapy startproject questions

相关文件简介：

scrapy.cfg: 项目的配置文件

questions/: 该项目的python模块。之后您将在此加入代码。

questions/items.py: 项目中的item文件.

questions/pipelines.py: 项目中的pipelines文件.

questions/settings.py: 项目的设置文件.

questions/spiders/: 放置spider代码的目录.

questions/spiders/xueersi.py: 实现爬虫的主体代码.

xueersi.py  爬虫主体

# -*- coding: utf-8 -*-
import scrapy
import time
import numpy
import re
from questions.items import QuestionsItem
class xueersiSpider(scrapy.Spider):
 name = "xueersi" # 爬虫名字
 allowed_domains = ["tiku.xueersi.com"] # 目标的域名
# 爬取的目标地址
 start_urls = [
   "http://tiku.xueersi.com/shiti/list_1_1_0_0_4_0_1",
   "http://tiku.xueersi.com/shiti/list_1_2_0_0_4_0_1",
   "http://tiku.xueersi.com/shiti/list_1_3_0_0_4_0_1",
 ]
 levels = ['偏易','中档','偏难']
 subjects = ['英语','语文','数学']
# 爬虫开始的时候，自动调用该方法，如果该方法不存在会自动调用parse方法
 # def start_requests(self):
 #   yield scrapy.Request('http://tiku.xueersi.com/shiti/list_1_2_0_0_4_0_39',callback=self.getquestion)
# start_requests方法不存在时，parse方法自动被调用
 def parse(self, response):
# xpath的选择器语法不多介绍，可以直接查看官方文档
   arr = response.xpath("//ul[@class='pagination']/li/a/text()").extract()
   total_page = arr[3]
# 获取分页
   for index in range(int(total_page)):
     yield scrapy.Request(response.url.replace('_0_0_4_0_1',"_0_0_4_0_"+str(index)),callback=self.getquestion) # 发出新的请求，获取每个分页所有题目
 # 获取题目
 def getquestion(self,response):
   for res in response.xpath('//div[@class="main-wrap"]/ul[@class="items"]/li'):
     item = QuestionsItem() # 实例化Item类
     # 获取问题
     questions = res.xpath('./div[@class="content-area"]').re(r'<div class="content-area">?([\s\S]+?)<(table|\/td|div|br)')
     if len(questions):
       # 获取题目
       question = questions[0].strip()
       item['source'] = question
       dr = re.compile(r'<[^>]+>',re.S)
       question = dr.sub('',question)
       content = res.extract()
       item['content'] = question
       # 获取课目
       subject = re.findall(ur'http:\/\/tiku\.xueersi\.com\/shiti\/list_1_(\d+)',response.url)
       item['subject'] = self.subjects[int(subject[0])-1]
       # 获取难度等级
       levels = res.xpath('//div[@class="info"]').re(ur'难度：([\s\S]+?)<')
       item['level'] = self.levels.index(levels[0])+1

# 获取选项
       options = re.findall(ur'[A-D][\.．]([\s\S]+?)<(\/td|\/p|br)',content)
       item['options'] = options
       if len(options):
         url = res.xpath('./div[@class="info"]/a/@href').extract()[0]
         request = scrapy.Request(url,callback=self.getanswer)
         request.meta['item'] = item # 缓存item数据，传递给下一个请求
         yield request
     #for option in options:
 # 获取答案      
 def getanswer(self,response):

res = response.xpath('//div[@class="part"]').re(ur'<td>([\s\S]+?)<\/td>')
   con = re.findall(ur'([\s\S]+?)<br>[\s\S]+?([A-D])',res[0]) # 获取含有解析的答案
   if con:
     answer = con[0][1]
     analysis = con[0][0] # 获取解析
   else:
     answer = res[0]
     analysis = ''
   if answer:
     item = response.meta['item'] # 获取item
     item['answer'] = answer.strip()
     item['analysis'] = analysis.strip()
     item['answer_url'] = response.url
     yield item # 返回item,输出管道（pipelines.py）会自动接收该数据

items.py 数据结构定义:

# -*- 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 QuestionsItem(scrapy.Item):
 content = scrapy.Field()
 subject = scrapy.Field()
 level = scrapy.Field()
 answer = scrapy.Field()
 options = scrapy.Field()
 analysis = scrapy.Field()
 source = scrapy.Field()
 answer_url = scrapy.Field()
 pass

pipelines.py 输出管道（本例子输出的数据写入本地数据库）：

# -*- 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 pymysql
import md5
class QuestionsPipeline(object):
 def __init__(self):
   # 建立数据库连接
   self.connect = pymysql.connect('localhost','root','','question',use_unicode=True,charset='utf8')
   # 获取游标
   self.cursor = self.connect.cursor()
   print("connecting mysql success!")
   self.answer = ['A','B','C','D']
 def process_item(self, item, spider):
   content = pymysql.escape_string(item['content'])
# 获取题目hash值，使用该字段过滤重复的题目
   m1 = md5.new()  
   m1.update(content)
   hash = m1.hexdigest()
   selectstr = "select id from question where hash='％s'"％(hash)
   self.cursor.execute(selectstr)
   res = self.cursor.fetchone()
   # 过滤相同的题目
   if not res:
# 插入题目
     sqlstr = "insert into question(content,source,subject,level,answer,analysis,hash,answer_url) VALUES('％s','％s','％s','％s','％s','％s','％s','％s')"％(content,pymysql.escape_string(item['source']),item['subject'],item['level'],item['answer'],pymysql.escape_string(item['analysis']),hash,item['answer_url'])
     self.cursor.execute(sqlstr)
     qid = self.cursor.lastrowid
# 插入选项
     for index in range(len(item['options'])):
       option = item['options'][index]
       answer = self.answer.index(item['answer'])
       if answer==index:
         ans = '2'
       else:
         ans = '1'
       sqlstr = "insert into options(content,qid,answer) VALUES('％s','％s','％s')"％(pymysql.escape_string(option[0]),qid,ans)
       self.cursor.execute(sqlstr)
     self.connect.commit()
     #self.connect.close()
   return item

爬虫构建完毕后，在项目的根目录下运行

scrapy crawl xueersi # scrapy crawl 爬虫的名称

来源：https://www.cnblogs.com/dudeyouth/p/8795409.html