scrapy框架开发爬虫实战——爬取图书信息案例

创建爬虫项目，名称：example。在命令行输入以下命令：

scrapy startproject example

创建一个爬虫，名称：books。在命令行输入以下命令：

scrapy crawl genspider book_spider books "books.toscrape.com/"

创建好的爬虫，目录结构如下：

 

编写爬虫文件 book_spider.py

# _*_ coding:utf-8 _*_
import scrapy

#注意是scrapy.Spider不是scrapy.spider
#用  scrapy crawl  -o books.csv  命令运行该爬虫


class BookSpider(scrapy.Spider):

    # 每个爬虫的唯一标志
    name = "books"

    # 定义爬虫爬取的起始点，起始点可以是多个，这里只有一个
    start_urls = ['http://books.toscrape.com/']

    def parse(self, response):
        # 提取数据
        # 每一本书的信息在 
中
        # css()方法找到所有这样的article元素，并以此迭代
        for book in response.css('article.product_pod'):
            # 书名信息在 article>h3>a元素的title属性里
            # 例如： A Light
            name = book.xpath('./h3/a/@title').extract_first()
            # 书价信息在 
的TEXT中
            # 例如：
51.77
            price = book.css('p.price_color::text').extract_first()
            yield {
                'name': name,
                'price': price
            }

    # 提取链接
    # 下一页的url在ul.pager>li.next>a里面
    # 例如：next
        next_url = response.css('ul.pager li.next a::attr(href)').extract_first()
        if next_url:
         # 如果找到下一页的url,得到绝对路径，构造新的Request对象
            next_url = response.urljoin(next_url)
            print(next_url)
            yield scrapy.Request(next_url)

编写pipelines.py文件

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

from scrapy.exceptions import  DropItem
from scrapy.item import Item
import pymongo

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


#class ExamplePipeline(object):
#   def process_item(self, item, spider):
#        return item

#处理数据
class PriceConverterPipeline(object):

    #英镑兑换人民币汇率
    exchange_rate=8.5309

    def process_item(self,item,spider):
        #提取item的price字段
        #去掉前面的英镑符号，转换为float类型，乘以汇率
        price =float(item['price'][1:])*self.exchange_rate

        #保留两位小数，赋值回item的price字段
        item['price']='Y%.2f'%price

        return item

#去重复数据
class DuplicatesPipeline(object):

    def __init__(self):
        self.book_set=set()

    def process_item(self,item,spider):
        name =item['name']
        if name in self.book_set:
            raise DropItem("Duplicate book found :%s"%item)
        self.book_set.add(name)
        return item


#将数据存入MongoDB
class MongoDBPipeline(object):

    #改变这种硬编码方式
    #DB_URI='mongodb://localhost:27017'
    #DB_URI='localhost'
    #DB_NAME='scrapy_data'

    #替换硬编码方式
    @classmethod
    def from_crawler(cls,crawler):
        cls.DB_URI=crawler.settings.get('MONGO_DB_URI')
        cls.DB_NAME=crawler.settings.get('MONGO_DB_NAME')
        return cls()

    def open_spider(self,spider):
        #连接MongoDB
        self.client = pymongo.MongoClient(self.DB_URI)
        self.db=self.client[self.DB_NAME]  #此处用中括号

    def close_spider(self,spider):
        #关闭MongoDB
        self.client.close()

    def process_item(self,item,spider):
        collection = self.db[spider.name]  #设置MongoBD的Collection名
        post=dict(item) if isinstance(item,Item) else item  #以dictde形式存入MongoDB
        collection.insert_one(post)  #将dict数据插入MongoDB
        return item

编写settings.py配置文件

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

# Scrapy settings for example project
#
# For simplicity, this file contains only settings considered important or
# commonly used. You can find more settings consulting the documentation:
#
#     https://docs.scrapy.org/en/latest/topics/settings.html
#     https://docs.scrapy.org/en/latest/topics/downloader-middleware.html
#     https://docs.scrapy.org/en/latest/topics/spider-middleware.html

BOT_NAME = 'example'

SPIDER_MODULES = ['example.spiders']
NEWSPIDER_MODULE = 'example.spiders'


# Crawl responsibly by identifying yourself (and your website) on the user-agent
#USER_AGENT = 'example (+http://www.yourdomain.com)'

# Obey robots.txt rules
ROBOTSTXT_OBEY = True

# Configure maximum concurrent requests performed by Scrapy (default: 16)
#CONCURRENT_REQUESTS = 32

# Configure a delay for requests for the same website (default: 0)
# See https://docs.scrapy.org/en/latest/topics/settings.html#download-delay
# See also autothrottle settings and docs
#DOWNLOAD_DELAY = 3
# The download delay setting will honor only one of:
#CONCURRENT_REQUESTS_PER_DOMAIN = 16
#CONCURRENT_REQUESTS_PER_IP = 16

# Disable cookies (enabled by default)
#COOKIES_ENABLED = False

# Disable Telnet Console (enabled by default)
#TELNETCONSOLE_ENABLED = False

# Override the default request headers:
#DEFAULT_REQUEST_HEADERS = {
#   'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
#   'Accept-Language': 'en',
#}

# Enable or disable spider middlewares
# See https://docs.scrapy.org/en/latest/topics/spider-middleware.html
#SPIDER_MIDDLEWARES = {
#    'example.middlewares.ExampleSpiderMiddleware': 543,
#}

# Enable or disable downloader middlewares
# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html
#DOWNLOADER_MIDDLEWARES = {
#    'example.middlewares.ExampleDownloaderMiddleware': 543,
#}

# Enable or disable extensions
# See https://docs.scrapy.org/en/latest/topics/extensions.html
#EXTENSIONS = {
#    'scrapy.extensions.telnet.TelnetConsole': None,
#}

# Configure item pipelines
# See https://docs.scrapy.org/en/latest/topics/item-pipeline.html
ITEM_PIPELINES = {
    'example.pipelines.PriceConverterPipeline': 300,
    'example.pipelines.DuplicatesPipeline': 350,
    'example.pipelines.MongoDBPipeline':400,
}

# Enable and configure the AutoThrottle extension (disabled by default)
# See https://docs.scrapy.org/en/latest/topics/autothrottle.html
#AUTOTHROTTLE_ENABLED = True
# The initial download delay
#AUTOTHROTTLE_START_DELAY = 5
# The maximum download delay to be set in case of high latencies
#AUTOTHROTTLE_MAX_DELAY = 60
# The average number of requests Scrapy should be sending in parallel to
# each remote server
#AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0
# Enable showing throttling stats for every response received:
#AUTOTHROTTLE_DEBUG = False

# Enable and configure HTTP caching (disabled by default)
# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html#httpcache-middleware-settings
#HTTPCACHE_ENABLED = True
#HTTPCACHE_EXPIRATION_SECS = 0
#HTTPCACHE_DIR = 'httpcache'
#HTTPCACHE_IGNORE_HTTP_CODES = []
#HTTPCACHE_STORAGE = 'scrapy.extensions.httpcache.FilesystemCacheStorage'

#将MongoDB数据库的连接信息存到配置文件中
MONGO_DB_URI='mongodb://localhost:27017/'
MONGO_DB_NAME='lhf_jlu_scrapy_data'

运行爬虫

#books是爬虫名字，-o books.csv是以csv文件的方式存储到本地
scrapy crawl books -o books.csv

运行结果

books.csv

name,price,_id
A Light in the Attic,Y441.64,5d5a4dfbc21f74f56708e8ef
Tipping the Velvet,Y458.45,5d5a4dfbc21f74f56708e8f0
Soumission,Y427.40,5d5a4dfbc21f74f56708e8f1
Sharp Objects,Y407.95,5d5a4dfbc21f74f56708e8f2
Sapiens: A Brief History of Humankind,Y462.63,5d5a4dfbc21f74f56708e8f3
The Requiem Red,Y193.22,5d5a4dfbc21f74f56708e8f4
The Dirty Little Secrets of Getting Your Dream Job,Y284.42,5d5a4dfbc21f74f56708e8f5
"The Coming Woman: A Novel Based on the Life of the Infamous Feminist, Victoria Woodhull",Y152.96,5d5a4dfbc21f74f56708e8f6
The Boys in the Boat: Nine Americans and Their Epic Quest for Gold at the 1936 Berlin Olympics,Y192.80,5d5a4dfbc21f74f56708e8f7
The Black Maria,Y444.89,5d5a4dfbc21f74f56708e8f8
"Starving Hearts (Triangular Trade Trilogy, #1)",Y119.35,5d5a4dfbc21f74f56708e8f9
Shakespeare's Sonnets,Y176.25,5d5a4dfbc21f74f56708e8fa
Set Me Free,Y148.95,5d5a4dfbc21f74f56708e8fb
Scott Pilgrim's Precious Little Life (Scott Pilgrim #1),Y446.08,5d5a4dfbc21f74f56708e8fc
Rip it Up and Start Again,Y298.75,5d5a4dfbc21f74f56708e8fd
"Our Band Could Be Your Life: Scenes from the American Indie Underground, 1981-1991",Y488.39,5d5a4dfbc21f74f56708e8fe
Olio,Y203.72,5d5a4dfbc21f74f56708e8ff