12.scrapy框架
一.Scrapy 框架简介
1.简介
Scrapy是用纯Python实现一个为了爬取网站数据、提取结构性数据而编写的应用框架，用途非常广泛。 框架的力量，用户只需要定制开发几个模块就可以轻松的实现一个爬虫，用来抓取网页内容以及各种图片，非常之方便。 Scrapy 使用了 Twisted'twɪstɪd异步网络框架来处理网络通讯，可以加快我们的下载速度，不用自己去实现异步框架，并且包含了各种中间件接口，可以灵活的完成各种需求
框架图如下：
流程：
Scrapy Engine(引擎): 负责Spider、ItemPipeline、Downloader、Scheduler中间的通讯，信号、数据传递等。
Scheduler(调度器): 它负责接受引擎发送过来的Request请求，并按照一定的方式进行整理排列，入队，当引擎需要时，交还给引擎。
Downloader（下载器）：负责下载Scrapy Engine(引擎)发送的所有Requests请求，并将其获取到的Responses交还给Scrapy Engine(引擎)，由引擎交给Spider来处理，
Spider（爬虫）：它负责处理所有Responses,从中分析提取数据，获取Item字段需要的数据，并将需要跟进的URL提交给引擎，再次进入Scheduler(调度器)，
Item Pipeline(管道)：它负责处理Spider中获取到的Item，并进行进行后期处理（详细分析、过滤、存储等）的地方.
Downloader Middlewares（下载中间件）：你可以当作是一个可以自定义扩展下载功能的组件。
Spider Middlewares（Spider中间件）：你可以理解为是一个可以自定扩展和操作引擎和Spider中间通信的功能组件（比如进入Spider的Responses;和从Spider出去的Requests）
2.用法步骤
1.新建项目 (scrapy startproject xxx)：新建一个新的爬虫项目 2.明确目标 （编写items.py）：明确你想要抓取的目标 3.制作爬虫 （spiders/xxspider.py）：制作爬虫开始爬取网页 4.存储内容 （pipelines.py）：设计管道存储爬取内容
3.安装
Windows 安装方式 Python 2 / 3 升级pip版本：pip install --upgrade pip 通过pip 安装 Scrapy 框架pip install Scrapy Ubuntu 需要9.10或以上版本安装方式 Python 2 / 3 安装非Python的依赖 sudo apt-get install python-dev python-pip libxml2-dev libxslt1-dev zlib1g-dev libffi-dev libssl-dev 通过pip 安装 Scrapy 框架 sudo pip install scrapy 安装后，只要在命令终端输入 scrapy，看到正确信息即可
二.快速入门
a.创建一个新的Scrapy项目。进入自定义的项目目录中，运行下列命令：
scrapy startproject qsbk #[qsbk]为项目名字
其中， qsbk为项目名称，可以看到将会创建一个 qsbk文件夹，目录结构大致如下： 下面来简单介绍一下各个主要文件的作用： scrapy.cfg ：项目的配置文件 qsbk/ ：项目的Python模块，将会从这里引用代码 qsbk/items.py ：项目的目标文件 qsbk/pipelines.py ：项目的管道文件 qsbk/settings.py ：项目的设置文件 qsbk/spiders/ ：存储爬虫代码目录
b.创建一个案例
使用命令创建一个爬虫，先进去qsbk目录
scrapy genspider qsbk_spider "qiushibaike.com" #qsbk_spider 是爬虫名，不能和项目名一样，[qiushibaike.com]为要爬取的域名，
创建了一个名字叫做qsbk_spider的爬虫，并且能爬取的网页只会限制在qiushibaike.com这个域名下
settings.py
# -*- coding: utf-8 -*- # Scrapy settings for qsbk project # # For simplicity, this file contains only settings considered important or # commonly used. You can find more settings consulting the documentation: # # https://doc.scrapy.org/en/latest/topics/settings.html # https://doc.scrapy.org/en/latest/topics/downloader-middleware.html # https://doc.scrapy.org/en/latest/topics/spider-middleware.html BOT_NAME = 'qsbk' SPIDER_MODULES = ['qsbk.spiders'] NEWSPIDER_MODULE = 'qsbk.spiders' # Crawl responsibly by identifying yourself (and your website) on the user-agent #USER_AGENT = 'qsbk (+http://www.yourdomain.com)' # Obey robots.txt rules ROBOTSTXT_OBEY = False # 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://doc.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', #} DEFAULT_REQUEST_HEADERS = { 'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8', 'Accept-Language': 'en', 'User-Agent':'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36' } # Enable or disable spider middlewares # See https://doc.scrapy.org/en/latest/topics/spider-middleware.html #SPIDER_MIDDLEWARES = { # 'qsbk.middlewares.QsbkSpiderMiddleware': 543, #} # Enable or disable downloader middlewares # See https://doc.scrapy.org/en/latest/topics/downloader-middleware.html #DOWNLOADER_MIDDLEWARES = { # 'qsbk.middlewares.QsbkDownloaderMiddleware': 543, #} # Enable or disable extensions # See https://doc.scrapy.org/en/latest/topics/extensions.html #EXTENSIONS = { # 'scrapy.extensions.telnet.TelnetConsole': None, #} # Configure item pipelines # See https://doc.scrapy.org/en/latest/topics/item-pipeline.html #ITEM_PIPELINES = { # 'qsbk.pipelines.QsbkPipeline': 300, #} # Enable and configure the AutoThrottle extension (disabled by default) # See https://doc.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://doc.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'
qsbk_spider.py
import scrapy class QsbkSpiderSpider(scrapy.Spider): name = 'qsbk_spider' allowed_domains = ['qiushibaike.com'] start_urls = ['https://www.qiushibaike.com/text/page/1/'] def parse(self, response): #SelectorList duanzidivs=response.xpath('//div[@id="content-left"]/div') for duanzidiv in duanzidivs: #Selector authors=duanzidiv.xpath('.//h2/text()').get().strip() content=duanzidiv.xpath('.//div[@class="content"]/span/text()').getall() content="".join(content) print(authors,content)
在qsbk目录下创建start.py
from scrapy import cmdline cmdline.execute(["scrapy","crawl","qsbk_spider"])
执行即可看到结果
c.保存数据
qsbk_spider.py
import scrapy from qsbk.items import QsbkItem class QsbkSpiderSpider(scrapy.Spider): name = 'qsbk_spider' allowed_domains = ['qiushibaike.com'] start_urls = ['https://www.qiushibaike.com/text/page/1/'] def parse(self, response): #SelectorList duanzidivs=response.xpath('//div[@id="content-left"]/div') items=[] for duanzidiv in duanzidivs: #Selector author=duanzidiv.xpath('.//h2/text()').get().strip() content=duanzidiv.xpath('.//div[@class="content"]/span/text()').getall() content="".join(content) item=QsbkItem(author=author,content=content) yield item #或者将此行注销，将下面两行的#去掉 # items.append(item) # return items #注意：提取出来的数据是一个Selector或者是一个SelectorList # getall()获取的是所有文本，返回的是一个列表，get()获取的是第一个文本，返回的是str
settings.py
DEFAULT_REQUEST_HEADERS = {
'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
'Accept-Language': 'en',
'User-Agent':'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36'
}
ROBOTSTXT_OBEY = False
ITEM_PIPELINES = { 'qsbk.pipelines.QsbkPipeline': 300, } #将此行的注释打开
pipelines.py
import json class QsbkPipeline(object): def __init__(self): self.fp=open("duanzi.json","w",encoding="utf-8") def open_spider(self,spider): print("开始了") def process_item(self, item, spider): item_json=json.dumps(dict(item),ensure_ascii=False) self.fp.write(item_json+"\n") return item def close_spider(self,spider): self.fp.close() print("结束了") #open_spider:当爬虫被打开的时候执行 #process_item：当爬虫有item传过来的时候被调用 #close_spider：当爬虫关闭的时候会被调用 #要激活pipline，应该再settings.py中，设置ITEM_PIPLINES
items.py
import scrapy class QsbkItem(scrapy.Item): # define the fields for your item here like: # name = scrapy.Field() author=scrapy.Field() content=scrapy.Field()
在qsbk目录下创建start.py
from scrapy import cmdline cmdline.execute(["scrapy","crawl","qsbk_spider"])
d.优化保存数据
pipelines.py
from scrapy.exporters import JsonItemExporter class QsbkPipeline(object): def __init__(self): self.fp=open("duanzi.json","wb") self.exporter=JsonItemExporter(self.fp,ensure_ascii=False,encoding="utf-8") self.exporter.start_exporting() def open_spider(self,spider): print("开始了") def process_item(self, item, spider): # item_json=json.dumps(dict(item),ensure_ascii=False) # self.fp.write(item_json+"\n") self.exporter.export_item(item) return item def close_spider(self,spider): self.exporter.finish_exporting() self.fp.close() print("结束了")
或者
from scrapy.exporters import JsonLinesItemExporter class QsbkPipeline(object): def __init__(self): self.fp=open("duanzi.json","wb") self.exporter=JsonLinesItemExporter(self.fp,ensure_ascii=False,encoding="utf-8") def open_spider(self,spider): print("开始了") def process_item(self, item, spider): # item_json=json.dumps(dict(item),ensure_ascii=False) # self.fp.write(item_json+"\n") self.exporter.export_item(item) return item def close_spider(self,spider): self.exporter.finish_exporting() self.fp.close() print("结束了")
其他不变
e.多次请求下一页
qsbk_spider.py
import scrapy from qsbk.items import QsbkItem class QsbkSpiderSpider(scrapy.Spider): name = 'qsbk_spider' allowed_domains = ['qiushibaike.com'] start_urls = ['https://www.qiushibaike.com/text/page/1/'] base_domain="https://www.qiushibaike.com" def parse(self, response): #SelectorList duanzidivs=response.xpath('//div[@id="content-left"]/div') items=[] for duanzidiv in duanzidivs: #Selector author=duanzidiv.xpath('.//h2/text()').get().strip() content=duanzidiv.xpath('.//div[@class="content"]/span/text()').getall() content="".join(content) item=QsbkItem(author=author,content=content) yield item #或者将此行注销，将下面两行的#去掉 # items.append(item) # return items next_url=response.xpath('//ul[@class="pagination"]/li[last()]/a/@href').get() if not next_url: return else: yield scrapy.Request(self.base_domain+next_url,callback=self.parse)
待
