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+"
")
        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+"
")
        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+"
")
        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