Scrapy

目录

一、简介

二、安装和基本使用

三. 选择器

四. 格式化和持久化处理(item+pipelines)

五.爬虫中间件

六. 自定制命令

七. 自定义扩展

八. 避免重复访问

九.配置文件和示例

一、简介

Scrapy是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。 其可以应用在数据挖掘，信息处理或存储历史数据等一系列的程序中。
其最初是为了页面抓取 (更确切来说, 网络抓取 )所设计的， 也可以应用在获取API所返回的数据(例如 Amazon Associates Web Services ) 或者通用的网络爬虫。Scrapy用途广泛，可以用于数据挖掘、监测和自动化测试。

Scrapy 使用了 Twisted异步网络库来处理网络通讯。整体架构大致如下

1、Scrapy主要包括了以下组件：

• 引擎(Scrapy)
  用来处理整个系统的数据流处理, 触发事务(框架核心)
• 调度器(Scheduler)
  用来接受引擎发过来的请求, 压入队列中, 并在引擎再次请求的时候返回. 可以想像成一个URL（抓取网页的网址或者说是链接）的优先队列, 由它来决定下一个要抓取的网址是什么, 同时去除重复的网址
• 下载器(Downloader)
  用于下载网页内容, 并将网页内容返回给蜘蛛(Scrapy下载器是建立在twisted这个高效的异步模型上的)
• 爬虫(Spiders)
  爬虫是主要干活的, 用于从特定的网页中提取自己需要的信息, 即所谓的实体(Item)。用户也可以从中提取出链接,让Scrapy继续抓取下一个页面
• 项目管道(Pipeline)
  负责处理爬虫从网页中抽取的实体，主要的功能是持久化实体、验证实体的有效性、清除不需要的信息。当页面被爬虫解析后，将被发送到项目管道，并经过几个特定的次序处理数据。
• 下载器中间件(Downloader Middlewares)
  位于Scrapy引擎和下载器之间的框架，主要是处理Scrapy引擎与下载器之间的请求及响应。
• 爬虫中间件(Spider Middlewares)
  介于Scrapy引擎和爬虫之间的框架，主要工作是处理蜘蛛的响应输入和请求输出。
• 调度中间件(Scheduler Middewares)
  介于Scrapy引擎和调度之间的中间件，从Scrapy引擎发送到调度的请求和响应。

2、Scrapy运行流程大概如下：

1. 引擎从调度器中取出一个链接(URL)用于接下来的抓取
2. 引擎把URL封装成一个请求(Request)传给下载器
3. 下载器把资源下载下来，并封装成应答包(Response)
4. 爬虫解析Response
5. 解析出实体（Item）,则交给实体管道进行进一步的处理
6. 解析出的是链接（URL）,则把URL交给调度器等待抓取

二、安装和基本使用

Linux
      pip3 install scrapy
 
 
Windows
      a. pip3 install wheel
      b. 下载twisted http://www.lfd.uci.edu/~gohlke/pythonlibs/#twisted
      c. 进入下载目录，执行 pip3 install Twisted‑17.1.0‑cp35‑cp35m‑win_amd64.whl
      d. pip3 install scrapy
      e. 下载并安装pywin32：https://sourceforge.net/projects/pywin32/files/

1. 基本命令

1. scrapy startproject 项目名称
   - 在当前目录中创建中创建一个项目文件（类似于Django）
 
2. scrapy genspider [-t template] <name> <domain>
   - 创建爬虫应用
   如：
      scrapy gensipider -t basic oldboy oldboy.com
      scrapy gensipider -t xmlfeed autohome autohome.com.cn
   PS:
      查看所有命令：scrapy gensipider -l
      查看模板命令：scrapy gensipider -d 模板名称
 
3. scrapy list
   - 展示爬虫应用列表
 
4. scrapy crawl 爬虫应用名称
   - 运行单独爬虫应用

2.项目结构以及爬虫应用简介

project_name/
   scrapy.cfg
   project_name/
       __init__.py
       items.py
       pipelines.py
       settings.py
       spiders/
           __init__.py
           爬虫1.py
           爬虫2.py
           爬虫3.py

文件说明：

• scrapy.cfg  项目的主配置信息。（真正爬虫相关的配置信息在settings.py文件中）
• items.py    设置数据存储模板，用于结构化数据，如：Django的Model
• pipelines    数据处理行为，如：一般结构化的数据持久化
• settings.py 配置文件，如：递归的层数、并发数，延迟下载等
• spiders      爬虫目录，如：创建文件，编写爬虫规则

注意：一般创建爬虫文件时，以网站域名命名

• 爬虫1.py

import scrapy
 
class XiaoHuarSpider(scrapy.spiders.Spider):
    name = "xiaohuar"                            # 爬虫名称 *****
    allowed_domains = ["xiaohuar.com"]  # 允许的域名，只能在这个域名内爬取
    start_urls = [
        "http://www.xiaohuar.com/hua/",   # 其实URL
    ]
 
    def parse(self, response):
        # 访问起始URL并获取结果后的回调函数

 3、 response参数中封装了很多参数

response.url
response.text
response.body
response.meta['depth']  # 当前深度,可以通过判断当前深度到了哪一层，来选择停止时间

4、关于Windows编码，如果在Windows上执行代码，输出response.text为空的话，就加上这一段代码

import sys,io
sys.stdout=io.TextIOWrapper(sys.stdout.buffer,encoding='gb18030')

5. 小试牛刀

import scrapy
from scrapy.selector import HtmlXPathSelector
from scrapy.http.request import Request
 
 
class DigSpider(scrapy.Spider):
    # 爬虫应用的名称，通过此名称启动爬虫命令
    name = "dig"
 
    # 允许的域名
    allowed_domains = ["chouti.com"]
 
    # 起始URL
    start_urls = [
        'http://dig.chouti.com/',
    ]
 
    has_request_set = {}
 
    def parse(self, response):
        print(response.url)
 
        hxs = HtmlXPathSelector(response)
        page_list = hxs.select('//div[@id="dig_lcpage"]//a[re:test(@href, "/all/hot/recent/d+")]/@href').extract()
        for page in page_list:
            page_url = 'http://dig.chouti.com%s' % page
            key = self.md5(page_url)
            if key in self.has_request_set:
                pass
            else:
                self.has_request_set[key] = page_url
                obj = Request(url=page_url, method='GET', callback=self.parse)
                yield obj
 
    @staticmethod
    def md5(val):
        import hashlib
        ha = hashlib.md5()
        ha.update(bytes(val, encoding='utf-8'))
        key = ha.hexdigest()
        return key

• 执行此爬虫文件，则在终端进入项目目录执行如下命令：

scrapy crawl dig --nolog
# 记得在settings.py文件中修改ROBOTSTXT_OBEY = False，否则什么都不打印

　　对于上述代码重要之处在于：

• Request是一个封装用户请求的类，在回调函数中yield该对象表示继续访问
• HtmlXpathSelector用于结构化HTML代码并提供选择器功能

三. 选择器

设置递归层数：

• settings.py中设置DEPTH_LIMIT = 1来指定“递归”的层数，0表示没有限制，1表示在当前页的基础上再多访问一层，比如首页10个页码，1就是访问1-14个页码

常用选择器：

import scrapy
import hashlib
from scrapy.http import Request
from scrapy.selector import Selector,HtmlXPathSelector

class ChoutiSpider(scrapy.Spider):
    name = 'chouti'
    allowed_domains = ['chouti.com']
    start_urls = ['http://dig.chouti.com/']
    visited_urls = set() # 对URL去重

    # 程序初始化的时候会自动执行self.parse方法
    # 如果你想修改parse方法，就要加上这一段源码，然后重新写parse方法
    # def start_requests(self):
    #     for url in self.start_urls:
    #         yield Request(url=url,callback=self.parse)


    def parse(self, response):
        # 找到所有的A标签对象列表
        # hxs = Selector(response=response).xpath('//a').extract()
        # for i in hxs:
        #     print(i)
        # //从所有文档标签中找，/从所有儿子中找，@后面加属性参数
        # hxs = Selector(response=response).xpath('//div[@id="content-list"]/div[@class="item"]')
        # for obj in hxs:
            # print(obj)
            # .//表示从当前对象的子孙中寻找，./表示从当前对象的儿子中找，如果有两个class都要写上，否则找不到
            # /text()获取文本，
            # extract（）把列表中每一个对象转换成字符串,
            # extract_first()把列表中每一个对象转换成字符串,并返回第一个元素
            # a = obj.xpath('.//a[@class="show-content color-chag"]/text()').extract_first()
            # print(a.strip())
        # 获取当前页的所有页码,/@属性名--获取标签对象的属性，/ul/li/a可以直接写//a
        # hxs = Selector(response=response).xpath('//div[@id="dig_lcpage"]//a/@href').extract()
        # starts-with寻找标签属性值是以什么开头的
        # hxs = Selector(response=response).xpath('//a[starts-with(@href, "/all/hot/recent/")]/@href').extract()
        # 正则表达式匹配re:test
        hxs = Selector(response=response).xpath('//a[re:test(@href, "/all/hot/recent/d+")]/@href').extract()
        for url in hxs:
            md5_url = self.md5(url)
            if md5_url in self.visited_urls:
                # 访问过的不管
                pass
            else:
                self.visited_urls.add(md5_url)
                print(url)# /all/hot/recent/10
                url = 'http://dig.chouti.com/%s'%url
                # 递归爬取所有页码，必须加yield，引擎帮我们将新要访问的URL放入调度器
                # 一次下载完成之后回调函数也可以是其他函数，但是就无法实现递归了，所以还是用parse
                yield Request(url=url,callback=self.parse)

    def md5(self,url):
        """如果URL特别长，数据库中建立索引费空间，所以先加密再放入"""
        obj = hashlib.md5()
        obj.update(bytes(url,encoding='utf-8'))
        return obj.hexdigest()

更多选择器：

from scrapy.selector import Selector, HtmlXPathSelector
from scrapy.http import HtmlResponse

html = """<!DOCTYPE html>
<html>
    <head lang="en">
        <meta charset="UTF-8">
        <title></title>
    </head>
    <body>
        <ul>
            <li class="item-"><a id='i1' href="link.html">first item</a></li>
            <li class="item-0"><a id='i2' href="llink.html">first item</a></li>
            <li class="item-1"><a href="llink2.html">second item<span>vv</span></a></li>
        </ul>
        <div><a href="llink2.html">second item</a></div>
    </body>
</html>
"""
response = HtmlResponse(url='http://example.com', body=html, encoding='utf-8')
hxs = HtmlXPathSelector(response)
print(hxs)
hxs = Selector(response=response).xpath('//a')# 找到所有的a标签
print(hxs)
hxs = Selector(response=response).xpath('//a[2]')# 找到列表里索引为2的标签
print(hxs)
hxs = Selector(response=response).xpath('//a[@id]')# 找到a标签中有id属性的所有标签
print(hxs)
hxs = Selector(response=response).xpath('//a[@id="i1"]')# 找到a标签id=i1的所有标签
print(hxs)
hxs = Selector(response=response).xpath('//a[@href="link.html"][@id="i1"]')# 写两个条件就是且的意思
print(hxs)
hxs = Selector(response=response).xpath('//a[contains(@href, "link")]')# a标签的href属性中包含link
print(hxs)
hxs = Selector(response=response).xpath('//a[starts-with(@href, "link")]')# a标签的href属性以xx开头
print(hxs)
hxs = Selector(response=response).xpath('//a[re:test(@id, "id+")]') # 正则表达式
print(hxs)
hxs = Selector(response=response).xpath('//a[re:test(@id, "id+")]/text()').extract() # 取标签对象的文本
print(hxs)
hxs = Selector(response=response).xpath('//a[re:test(@id, "id+")]/@href').extract()# 取标签对象的href属性
print(hxs)
hxs = Selector(response=response).xpath('/html/body/ul/li/a/@href').extract()# /一个孩子一个孩子的找，不会越级
print(hxs)
hxs = Selector(response=response).xpath('//body/ul/li/a/@href').extract_first()
print(hxs)

ul_list = Selector(response=response).xpath('//body/ul/li')
for item in ul_list:
    v = item.xpath('./a/span')# 从当前对象的儿子中找
    # 或
    # v = item.xpath('a/span')
    # 或
    # v = item.xpath('*/a/span')
    print(v)

四. 格式化和持久化处理(item+pipelines)

1、上述实例只是简单的处理，所以在parse方法中直接处理。如果对于想要获取更多的数据处理，则可以利用Scrapy的items将数据格式化，然后统一交由pipelines来处理。

• Spider01/spiders/xiaohuar.py

# -*- coding: utf-8 -*-
import scrapy
from scrapy.selector import Selector
from ..items import XiaohuaItem
import hashlib
from scrapy.http import Request

class XiaohuarSpider(scrapy.Spider):
    name = 'xiaohuar'
    allowed_domains = ['xiaohuar.com']
    start_urls = ['http://www.xiaohuar.com/hua']
    visited_urls = set()

    def parse(self, response):
        items = Selector(response=response).xpath('//div[@class="item_list infinite_scroll"]/div')
        for obj in items:
            src = obj.xpath('.//div[@class="img"]/a/img/@src').extract_first()
            name = obj.xpath('.//div[@class="img"]/span/text()').extract_first()
            school = obj.xpath('.//div[@class="img"]/div/a/text()').extract_first()
            # print(school)
            if 'http' in src:
                url = src
            else:
                url = 'http://www.xiaohuar.com%s' % src
            item_obj = XiaohuaItem(name=name,url=url,school=school)
            yield item_obj

        urls = Selector(response=response).xpath('//a[re:test(@href,"http://www.xiaohuar.com/list-1-d+.html")]/@href').extract()
        for url in urls:
            md5_url = self.md5(url)
            if md5_url in self.visited_urls:
                pass
            else:
                self.visited_urls.add(md5_url)
                yield Request(url=url,callback=self.parse)


    def md5(self, url):
        """如果URL特别长，数据库中建立索引费空间，所以先加密再放入"""
        obj = hashlib.md5()
        obj.update(bytes(url, encoding='utf-8'))
        return obj.hexdigest()

• items

class XiaohuaItem(scrapy.Item):
    name = scrapy.Field()
    school = scrapy.Field()
    url = scrapy.Field()

• piplines

import requests
import os

class JsonPipeline(object):
    """保存到json文件"""
    def process_item(self, item, spider):
        # if spider.name == 'chouti':
        tpl = '%s
%s
%s

'%(item['school'],item['name'],item['url'])
        # print(tpl)
        file = open('files/xiaohuar.json', 'a')
        file.write(tpl)
        file.close()
        return item

class FilePipeline(object):
    """保存图片"""
    def __init__(self):
        if not os.path.exists('imgs'):
            os.makedirs('imgs')
    def process_item(self, item, spider):
        response = requests.get(url=item['url'],stream=True)
        file_name = '%s-%s.jpg'%(item['school'],item['name'])
        with open(os.path.join('imgs',file_name),'wb') as f:
            f.write(response.content)
        return item

• settings.py

ITEM_PIPELINES = {
   'spider1.pipelines.JsonPipeline': 100,
   'spider1.pipelines.FilePipeline': 300,
}
# 每行后面的整型值，确定了他们运行的顺序，item按数字从低到高的顺序，通过pipeline，通常将这些数字定义在0-1000范围内。

2、对于pipeline可以做更多，自定义pipeline：

import requests
import os
from scrapy.exceptions import DropItem

class JsonPipeline(object):
    """保存到json文件"""

    def __init__(self, conn_str):
        self.conn_str = conn_str
        self.conn = None

    def process_item(self, item, spider):
        """
        操作并进行持久化
        return item 表示会被后续的pipeline继续处理
        raise DropItem() 表示将item丢弃，不会被后续pipeline处理
        要么返回item，要么抛出丢弃异常
        """
        tpl = '%s
%s

'%(item['title'],item['href'])
        self.conn.write(tpl)
        return item

    @classmethod
    def from_crawler(cls, crawler):
        """
        初始化时候，用于创建pipeline对象,拿到配置文件中的文件路径
        :param crawler:
        :return:
        """
        conn_str = crawler.settings.get('DB')
        return cls(conn_str)

    def open_spider(self, spider):
        """
        爬虫开始执行时，调用，打开文件，只需要打开一次
        :param spider:
        :return:
        """
        self.conn = open(self.conn_str,'a')
        print('open...')

    def close_spider(self, spider):
        """
        爬虫关闭时，被调用，关闭文件
        :param spider:
        :return:
        """
        self.conn.close()
        print('close...')

# 配置文件中写上，DB必须大写
DB = 'files/chouti.json'

五.爬虫中间件

• 爬虫中间件

class SpiderMiddleware(object):

    def process_spider_input(self,response, spider):
        """
        下载完成，执行，然后交给parse处理
        :param response: 
        :param spider: 
        :return: 
        """
        pass

    def process_spider_output(self,response, result, spider):
        """
        spider处理完成，返回时调用
        :param response:
        :param result:
        :param spider:
        :return: 必须返回包含 Request 或 Item 对象的可迭代对象(iterable)
        """
        return result

    def process_spider_exception(self,response, exception, spider):
        """
        异常调用
        :param response:
        :param exception:
        :param spider:
        :return: None,继续交给后续中间件处理异常；含 Response 或 Item 的可迭代对象(iterable)，交给调度器或pipeline
        """
        return None


    def process_start_requests(self,start_requests, spider):
        """
        爬虫启动时调用
        :param start_requests:
        :param spider:
        :return: 包含 Request 对象的可迭代对象
        """
        return start_requests

• 下载器中间件

class DownMiddleware1(object):
    def process_request(self, request, spider):
        """
        请求需要被下载时，经过所有下载器中间件的process_request调用
        :param request: 
        :param spider: 
        :return:  
            None,继续后续中间件去下载；
            Response对象，停止process_request的执行，开始执行process_response
            Request对象，停止中间件的执行，将Request重新调度器
            raise IgnoreRequest异常，停止process_request的执行，开始执行process_exception
        """
        pass



    def process_response(self, request, response, spider):
        """
        spider处理完成，返回时调用
        :param response:
        :param result:
        :param spider:
        :return: 
            Response 对象：转交给其他中间件process_response
            Request 对象：停止中间件，request会被重新调度下载
            raise IgnoreRequest 异常：调用Request.errback
        """
        print('response1')
        return response

    def process_exception(self, request, exception, spider):
        """
        当下载处理器(download handler)或 process_request() (下载中间件)抛出异常
        :param response:
        :param exception:
        :param spider:
        :return: 
            None：继续交给后续中间件处理异常；
            Response对象：停止后续process_exception方法
            Request对象：停止中间件，request将会被重新调用下载
        """
        return None

六. 自定制命令

• 在spiders同级创建任意目录，如：commands
• 在其中创建 crawlall.py 文件 （此处文件名就是自定义的命令）

from scrapy.commands import ScrapyCommand
from scrapy.utils.project import get_project_settings

    class Command(ScrapyCommand):

        requires_project = True

        def syntax(self):
            return '[options]'

        def short_desc(self):
            return 'Runs all of the spiders'

        def run(self, args, opts):
            """
            self.crawler_process是CrawlerProcess的对象，包含所有的爬虫和配置文件
            执行CrawlerProcess的构造方法，
            获取所有的爬虫列表
            """
            # spider_list = ['chouti','cbblogs']可以随意控制运行的爬虫
            spider_list = self.crawler_process.spiders.list()
            for name in spider_list:
                self.crawler_process.crawl(name, **opts.__dict__)
            self.crawler_process.start()    

• 在settings.py 中添加配置 COMMANDS_MODULE = '项目名称.目录名称'

• 在项目目录执行命令：scrapy crawlall 

# 单个爬虫
import sys
from scrapy.cmdline import execute

if __name__ == '__main__':
    execute(["scrapy","github","--nolog"])

七. 自定义扩展

自定义扩展时，利用信号在指定位置注册指定操作

修改配置文件：

EXTENSIONS = {
   'Spider01.extention.MyExtension': 300,
}

from scrapy import signals


class MyExtension(object):
    def __init__(self, value):
        self.value = value

    @classmethod
    def from_crawler(cls, crawler):
        val = crawler.settings.getint('MMMM')
        obj = cls(val)

        crawler.signals.connect(obj.spider_opened, signal=signals.spider_opened)
        crawler.signals.connect(obj.spider_closed, signal=signals.spider_closed)

        return obj

    def spider_opened(self, spider):
        print('open')

    def spider_closed(self, spider):
        print('close')

八. 避免重复访问

scrapy默认使用 scrapy.dupefilter.RFPDupeFilter 进行去重，相关配置有：

DUPEFILTER_CLASS = 'scrapy.dupefilter.RFPDupeFilter'
DUPEFILTER_DEBUG = False
JOBDIR = "保存范文记录的日志路径，如：/root/"  # 最终路径为 /root/requests.seen

•   自定义URL去重操作

class RepeatUrl:
    def __init__(self):
        self.visited_url = set()

    @classmethod
    def from_settings(cls, settings):
        """
        初始化时，调用
        :param settings: 
        :return: 
        """
        return cls()

    def request_seen(self, request):
        """
        检测当前请求是否已经被访问过
        :param request: 
        :return: True表示已经访问过；False表示未访问过
        """
        if request.url in self.visited_url:
            return True
        self.visited_url.add(request.url)
        return False

    def open(self):
        """
        开始爬去请求时，调用
        :return: 
        """
        print('open replication')

    def close(self, reason):
        """
        结束爬虫爬取时，调用
        :param reason: 
        :return: 
        """
        print('close replication')

    def log(self, request, spider):
        """
        记录日志
        :param request: 
        :param spider: 
        :return: 
        """
        print('repeat', request.url)

九.配置文件和示例

• settings.py

# 1. 爬虫名称
BOT_NAME = 'step8_king'

# 2. 爬虫应用路径
SPIDER_MODULES = ['step8_king.spiders']
NEWSPIDER_MODULE = 'step8_king.spiders'

# Crawl responsibly by identifying yourself (and your website) on the user-agent
# 3. 客户端 user-agent请求头
# USER_AGENT = 'step8_king (+http://www.yourdomain.com)'
# 可以改成浏览器
#USER_AGENT = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.98 Safari/537.36'


# Obey robots.txt rules
# 4. 禁止爬虫配置，就是不遵循爬虫限制规则
# ROBOTSTXT_OBEY = False

# Configure maximum concurrent requests performed by Scrapy (default: 16)
# 5. 并发请求数，最大32个爬虫一起
# CONCURRENT_REQUESTS = 4

# Configure a delay for requests for the same website (default: 0)
# See http://scrapy.readthedocs.org/en/latest/topics/settings.html#download-delay
# See also autothrottle settings and docs
# 6. 延迟下载秒数，每2秒执行一个，太快容易被封号
# DOWNLOAD_DELAY = 2


# The download delay setting will honor only one of:
# 7. 单域名访问并发数，并且延迟下次秒数也应用在每个域名
# CONCURRENT_REQUESTS_PER_DOMAIN = 2
# 单IP访问并发数，如果有值则忽略：CONCURRENT_REQUESTS_PER_DOMAIN，并且延迟下次秒数也应用在每个IP
# CONCURRENT_REQUESTS_PER_IP = 3

# Disable cookies (enabled by default)
# 8. 是否支持cookie，cookiejar进行操作cookie
# COOKIES_ENABLED = True 默认表示支持
# COOKIES_DEBUG = True 是否是调试模式

# Disable Telnet Console (enabled by default)
# 9. Telnet用于查看当前爬虫的信息，操作爬虫等...
#    使用telnet ip port ，然后通过命令操作
# TELNETCONSOLE_ENABLED = True
# TELNETCONSOLE_HOST = '127.0.0.1'
# TELNETCONSOLE_PORT = [6023,] #scrapy默认端口


# 10. 默认请求头
# 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',
# }


# Configure item pipelines
# See http://scrapy.readthedocs.org/en/latest/topics/item-pipeline.html
# 11. 定义pipeline处理请求的优先级，权重越大优先级越低
# ITEM_PIPELINES = {
#    'step8_king.pipelines.JsonPipeline': 700,后执行
#    'step8_king.pipelines.FilePipeline': 500, 先执行
# }



# 12. 自定义扩展，基于信号进行调用
# 自定义类，重写signals中规定的方法，把自己的方法注册到signals
# Enable or disable extensions
# See http://scrapy.readthedocs.org/en/latest/topics/extensions.html
# EXTENSIONS = {
#     # 'step8_king.extensions.MyExtension': 500,
# }


# 13. 爬虫允许的最大深度，可以通过meta查看当前深度；0表示无深度
# DEPTH_LIMIT = 3

# 14. 爬取时，0表示深度优先Lifo(默认)；1表示广度优先FiFo

# 后进先出，深度优先
# DEPTH_PRIORITY = 0
# SCHEDULER_DISK_QUEUE = 'scrapy.squeue.PickleLifoDiskQueue'
# SCHEDULER_MEMORY_QUEUE = 'scrapy.squeue.LifoMemoryQueue'
# 先进先出，广度优先

# DEPTH_PRIORITY = 1
# SCHEDULER_DISK_QUEUE = 'scrapy.squeue.PickleFifoDiskQueue'
# SCHEDULER_MEMORY_QUEUE = 'scrapy.squeue.FifoMemoryQueue'

# 15. 调度器队列
# SCHEDULER = 'scrapy.core.scheduler.Scheduler'
# from scrapy.core.scheduler import Scheduler


# 16. 访问URL去重
# DUPEFILTER_CLASS = 'step8_king.duplication.RepeatUrl'


# Enable and configure the AutoThrottle extension (disabled by default)
# See http://doc.scrapy.org/en/latest/topics/autothrottle.html

"""
17. 自动限速算法
    from scrapy.contrib.throttle import AutoThrottle
    自动限速设置
    1. 获取最小延迟 DOWNLOAD_DELAY
    2. 获取最大延迟 AUTOTHROTTLE_MAX_DELAY
    3. 设置初始下载延迟 AUTOTHROTTLE_START_DELAY
    4. 当请求下载完成后，获取其"连接"时间 latency，即：请求连接到接受到响应头之间的时间
    5. 用于计算的... AUTOTHROTTLE_TARGET_CONCURRENCY
    target_delay = latency / self.target_concurrency
    new_delay = (slot.delay + target_delay) / 2.0 #计算下一次的延迟时间
    new_delay = max(target_delay, new_delay)
    new_delay = min(max(self.mindelay, new_delay), self.maxdelay)
    slot.delay = new_delay
"""

# 开始自动限速
# AUTOTHROTTLE_ENABLED = True
# The initial download delay
# 初始下载延迟
# AUTOTHROTTLE_START_DELAY = 5
# The maximum download delay to be set in case of high latencies
# 最大下载延迟
# AUTOTHROTTLE_MAX_DELAY = 10
# The average number of requests Scrapy should be sending in parallel to each remote server
# 平均每秒并发数
# AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0

# Enable showing throttling stats for every response received:
# 是否显示
# AUTOTHROTTLE_DEBUG = True

# Enable and configure HTTP caching (disabled by default)
# See http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html#httpcache-middleware-settings


"""
18. 启用缓存
    目的用于将已经发送的请求或相应缓存下来，以便以后使用
    
    from scrapy.downloadermiddlewares.httpcache import HttpCacheMiddleware
    from scrapy.extensions.httpcache import DummyPolicy
    from scrapy.extensions.httpcache import FilesystemCacheStorage
"""
# 是否启用缓存策略
# HTTPCACHE_ENABLED = True

# 缓存策略：所有请求均缓存，下次在请求直接访问原来的缓存即可
# HTTPCACHE_POLICY = "scrapy.extensions.httpcache.DummyPolicy"
# 缓存策略：根据Http响应头：Cache-Control、Last-Modified 等进行缓存的策略
# HTTPCACHE_POLICY = "scrapy.extensions.httpcache.RFC2616Policy"

# 缓存超时时间
# HTTPCACHE_EXPIRATION_SECS = 0

# 缓存保存路径
# HTTPCACHE_DIR = 'httpcache'

# 缓存忽略的Http状态码
# HTTPCACHE_IGNORE_HTTP_CODES = []

# 缓存存储的插件
# HTTPCACHE_STORAGE = 'scrapy.extensions.httpcache.FilesystemCacheStorage'


"""
19. 代理，需要在环境变量中设置
    from scrapy.contrib.downloadermiddleware.httpproxy import HttpProxyMiddleware
    
    方式一：使用默认
        os.environ
        {
            http_proxy:http://root:woshiniba@192.168.11.11:9999/
            https_proxy:http://192.168.11.11:9999/
        }
    方式二：使用自定义下载中间件
    
    def to_bytes(text, encoding=None, errors='strict'):
        if isinstance(text, bytes):
            return text
        if not isinstance(text, six.string_types):
            raise TypeError('to_bytes must receive a unicode, str or bytes '
                            'object, got %s' % type(text).__name__)
        if encoding is None:
            encoding = 'utf-8'
        return text.encode(encoding, errors)
        
    class ProxyMiddleware(object):
        def process_request(self, request, spider):
            PROXIES = [
                {'ip_port': '111.11.228.75:80', 'user_pass': ''},
                {'ip_port': '120.198.243.22:80', 'user_pass': ''},
                {'ip_port': '111.8.60.9:8123', 'user_pass': ''},
                {'ip_port': '101.71.27.120:80', 'user_pass': ''},
                {'ip_port': '122.96.59.104:80', 'user_pass': ''},
                {'ip_port': '122.224.249.122:8088', 'user_pass': ''},
            ]
            proxy = random.choice(PROXIES)
            if proxy['user_pass'] is not None:
                request.meta['proxy'] = to_bytes（"http://%s" % proxy['ip_port']）
                encoded_user_pass = base64.encodestring(to_bytes(proxy['user_pass']))
                request.headers['Proxy-Authorization'] = to_bytes('Basic ' + encoded_user_pass)
                print "**************ProxyMiddleware have pass************" + proxy['ip_port']
            else:
                print "**************ProxyMiddleware no pass************" + proxy['ip_port']
                request.meta['proxy'] = to_bytes("http://%s" % proxy['ip_port'])
    
    DOWNLOADER_MIDDLEWARES = {
       'step8_king.middlewares.ProxyMiddleware': 500,
    }
    
"""

"""
20. Https访问
    Https访问时有两种情况：
    1. 要爬取网站使用的可信任证书(默认支持)
        DOWNLOADER_HTTPCLIENTFACTORY = "scrapy.core.downloader.webclient.ScrapyHTTPClientFactory"
        DOWNLOADER_CLIENTCONTEXTFACTORY = "scrapy.core.downloader.contextfactory.ScrapyClientContextFactory"
        
    2. 要爬取网站使用的自定义证书
        DOWNLOADER_HTTPCLIENTFACTORY = "scrapy.core.downloader.webclient.ScrapyHTTPClientFactory"
        DOWNLOADER_CLIENTCONTEXTFACTORY = "step8_king.https.MySSLFactory"
        
        # https.py
        from scrapy.core.downloader.contextfactory import ScrapyClientContextFactory
        from twisted.internet.ssl import (optionsForClientTLS, CertificateOptions, PrivateCertificate)
        
        class MySSLFactory(ScrapyClientContextFactory):
            def getCertificateOptions(self):
                from OpenSSL import crypto
                v1 = crypto.load_privatekey(crypto.FILETYPE_PEM, open('/Users/wupeiqi/client.key.unsecure', mode='r').read())
                v2 = crypto.load_certificate(crypto.FILETYPE_PEM, open('/Users/wupeiqi/client.pem', mode='r').read())
                return CertificateOptions(
                    privateKey=v1,  # pKey对象
                    certificate=v2,  # X509对象
                    verify=False,
                    method=getattr(self, 'method', getattr(self, '_ssl_method', None))
                )
    其他：
        相关类
            scrapy.core.downloader.handlers.http.HttpDownloadHandler
            scrapy.core.downloader.webclient.ScrapyHTTPClientFactory
            scrapy.core.downloader.contextfactory.ScrapyClientContextFactory
        相关配置
            DOWNLOADER_HTTPCLIENTFACTORY
            DOWNLOADER_CLIENTCONTEXTFACTORY

"""



"""
21. 爬虫中间件
    class SpiderMiddleware(object):

        def process_spider_input(self,response, spider):
            '''
            下载完成，执行，然后交给parse处理
            :param response: 
            :param spider: 
            :return: 
            '''
            pass
    
        def process_spider_output(self,response, result, spider):
            '''
            spider处理完成，返回时调用
            :param response:
            :param result:
            :param spider:
            :return: 必须返回包含 Request 或 Item 对象的可迭代对象(iterable)
            '''
            return result
    
        def process_spider_exception(self,response, exception, spider):
            '''
            异常调用
            :param response:
            :param exception:
            :param spider:
            :return: None,继续交给后续中间件处理异常；含 Response 或 Item 的可迭代对象(iterable)，交给调度器或pipeline
            '''
            return None
    
    
        def process_start_requests(self,start_requests, spider):
            '''
            爬虫启动时调用
            :param start_requests:
            :param spider:
            :return: 包含 Request 对象的可迭代对象
            '''
            return start_requests
    
    内置爬虫中间件：
        'scrapy.contrib.spidermiddleware.httperror.HttpErrorMiddleware': 50,
        'scrapy.contrib.spidermiddleware.offsite.OffsiteMiddleware': 500,
        'scrapy.contrib.spidermiddleware.referer.RefererMiddleware': 700,
        'scrapy.contrib.spidermiddleware.urllength.UrlLengthMiddleware': 800,
        'scrapy.contrib.spidermiddleware.depth.DepthMiddleware': 900,

"""
# from scrapy.contrib.spidermiddleware.referer import RefererMiddleware
# Enable or disable spider middlewares
# See http://scrapy.readthedocs.org/en/latest/topics/spider-middleware.html
SPIDER_MIDDLEWARES = {
   # 'step8_king.middlewares.SpiderMiddleware': 543,
}


"""
22. 下载中间件
    class DownMiddleware1(object):
        def process_request(self, request, spider):
            '''
            请求需要被下载时，经过所有下载器中间件的process_request调用
            :param request:
            :param spider:
            :return:
                None,继续后续中间件去下载；
                Response对象，停止process_request的执行，开始执行process_response
                Request对象，停止中间件的执行，将Request重新调度器
                raise IgnoreRequest异常，停止process_request的执行，开始执行process_exception
            '''
            pass
    
    
    
        def process_response(self, request, response, spider):
            '''
            spider处理完成，返回时调用
            :param response:
            :param result:
            :param spider:
            :return:
                Response 对象：转交给其他中间件process_response
                Request 对象：停止中间件，request会被重新调度下载
                raise IgnoreRequest 异常：调用Request.errback
            '''
            print('response1')
            return response
    
        def process_exception(self, request, exception, spider):
            '''
            当下载处理器(download handler)或 process_request() (下载中间件)抛出异常
            :param response:
            :param exception:
            :param spider:
            :return:
                None：继续交给后续中间件处理异常；
                Response对象：停止后续process_exception方法
                Request对象：停止中间件，request将会被重新调用下载
            '''
            return None

    
    默认下载中间件
    {
        'scrapy.contrib.downloadermiddleware.robotstxt.RobotsTxtMiddleware': 100,
        'scrapy.contrib.downloadermiddleware.httpauth.HttpAuthMiddleware': 300,
        'scrapy.contrib.downloadermiddleware.downloadtimeout.DownloadTimeoutMiddleware': 350,
        'scrapy.contrib.downloadermiddleware.useragent.UserAgentMiddleware': 400,
        'scrapy.contrib.downloadermiddleware.retry.RetryMiddleware': 500,
        'scrapy.contrib.downloadermiddleware.defaultheaders.DefaultHeadersMiddleware': 550,
        'scrapy.contrib.downloadermiddleware.redirect.MetaRefreshMiddleware': 580,
        'scrapy.contrib.downloadermiddleware.httpcompression.HttpCompressionMiddleware': 590,
        'scrapy.contrib.downloadermiddleware.redirect.RedirectMiddleware': 600,
        'scrapy.contrib.downloadermiddleware.cookies.CookiesMiddleware': 700,
        'scrapy.contrib.downloadermiddleware.httpproxy.HttpProxyMiddleware': 750,
        'scrapy.contrib.downloadermiddleware.chunked.ChunkedTransferMiddleware': 830,
        'scrapy.contrib.downloadermiddleware.stats.DownloaderStats': 850,
        'scrapy.contrib.downloadermiddleware.httpcache.HttpCacheMiddleware': 900,
    }

"""
# from scrapy.contrib.downloadermiddleware.httpauth import HttpAuthMiddleware
# Enable or disable downloader middlewares
# See http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html
# DOWNLOADER_MIDDLEWARES = {
#    'step8_king.middlewares.DownMiddleware1': 100,
#    'step8_king.middlewares.DownMiddleware2': 500,
# }

11、给抽屉点赞（带上Cookie）

• DEPTH_LIMIT不能等于1，会返回空，不知道为什么

# -*- coding: utf-8 -*-
import scrapy
from scrapy.http import Request
from scrapy.selector import Selector
from scrapy.http.cookies import CookieJar


class ChoutiSpider(scrapy.Spider):
    name = 'chouti'
    allowed_domains = ['chouti.com']
    start_urls = ['https://dig.chouti.com/']
    cookie_dict = None


    def parse(self, response):
        """
        response.request表示当前的请求对象
        cookie_obj._cookies表示获取的所有的cookies
        """
        cookie_obj = CookieJar()
        cookie_obj.extract_cookies(response,response.request)
        self.cookie_dict = cookie_obj._cookies
        # print(cookie_obj._cookies)
        # 带上cookie+用户名密码登陆,给任务调度器发送请求
        yield Request(
            url='https://dig.chouti.com/login',
            method='POST',
            body="phone=86155&password=123&oneMonth=1",# 不支持字典格式
            cookies=self.cookie_dict,
            headers= { 'content-type': 'application/x-www-form-urlencoded; charset=UTF-8',},
            callback=self.check_login,
        )

    def check_login(self,response):
        print(response.text)
        #{"result":{"code":"9999", "message":"", "data":{"complateReg":"0","destJid":"cdu_55306581825"}}}
        # 登陆成功后访问首页,访问首页不用带cookies
        yield Request(
            url='https://dig.chouti.com/',
            callback=self.good,
        )

    def good(self,response):
        """
        给所有指定页码的新闻点赞
        注意：DEPTH_LIMIT不能等于1，会返回空，不知道为什么
        """
        # 先找到所有的新闻ID列表
        id_list = Selector(response=response).xpath('//div[@share-linkid]/@share-linkid').extract()
        print(id_list)
        for nid in id_list:
            url = 'https://dig.chouti.com/link/vote?linksId=%s'%nid
            yield Request(
                url=url,
                cookies=self.cookie_dict,
                method='POST',
                callback=self.show,
            )

        # 递归获取当前页的所有页码，执行点赞请求
        page_urls = Selector(response=response).xpath('//div[@id="dig_lcpage"]//a/@href').extract()
        for page in page_urls:
            url = 'http://dig.chouti.com%s' % page
            yield Request(url=url, callback=self.good)

    def show(self,response):
        """显示点赞结果"""
        print(response.text)
        #{"result":{"code":"30010", "message":"你已经推荐过了", "data":""}}

12. 大文件下载

示例文件：猛击下载

13.TinyScrapy

from twisted.web.client import getPage  # 用于创建socket对象(如果下载完成，自动从事件循环中移除）
from twisted.internet import reactor   # 事件循环（所有的socket都已经移除，才会终止循环）
from twisted.internet import defer   # defer.Deferred特殊的socket对象，不会发请求，需要手动移除


def callback(arg):
    print('回来一个', arg)

@defer.inlineCallbacks
def task(url):
    # 1.利用getPage创建socket对象
    ret = getPage(bytes(url, encoding='utf8'))
    # 添加回调函数
    ret.addCallback(callback)
    # 2.将socket添加到事件循环
    yield ret

def stop(arg):
    print('已经全部现在完毕', arg)
    reactor.stop()

#3.开始事件循环
url_list = ['http://www.bing.com', 'http://www.baidu.com', ]
defer_list = []
for url in url_list:
    ret = task(url)
    defer_list.append(ret)

# 所有的socket请求完成后，终止循环
d = defer.DeferredList(defer_list)
d.addBoth(stop)

reactor.run()

from twisted.internet import defer
from twisted.web.client import getPage
from twisted.internet import reactor
import threading


def _next_request():
    _next_request_from_scheduler()


def _next_request_from_scheduler():
    ret = getPage(bytes('http://www.chouti.com', encoding='utf8'))
    ret.addCallback(callback)
    ret.addCallback(lambda _: reactor.callLater(0, _next_request))


_closewait = None

@defer.inlineCallbacks
def engine_start():
    global _closewait
    _closewait = defer.Deferred()
    yield _closewait


@defer.inlineCallbacks
def task(url):
    reactor.callLater(0, _next_request)
    yield engine_start()


counter = 0
def callback(arg):
    global counter
    counter +=1
    if counter == 10:
        _closewait.callback(None)
    print('one', len(arg))


def stop(arg):
    print('all done', arg)
    reactor.stop()


if __name__ == '__main__':
    url = 'http://www.cnblogs.com'

    defer_list = []
    deferObj = task(url)
    defer_list.append(deferObj)

    v = defer.DeferredList(defer_list)
    v.addBoth(stop)
    reactor.run()

from twisted.web.client import getPage, defer
from twisted.internet import reactor
import queue


class Response(object):
    def __init__(self, body, request):
        self.body = body
        self.request = request
        self.url = request.url

    @property
    def text(self):
        return self.body.decode('utf-8')


class Request(object):
    def __init__(self, url, callback=None):
        self.url = url
        self.callback = callback


class Scheduler(object):
    def __init__(self, engine):
        self.q = queue.Queue()
        self.engine = engine

    def enqueue_request(self, request):
        self.q.put(request)

    def next_request(self):
        try:
            req = self.q.get(block=False)
        except Exception as e:
            req = None

        return req

    def size(self):
        return self.q.qsize()


class ExecutionEngine(object):
    def __init__(self):
        self._closewait = None
        self.running = True
        self.start_requests = None
        self.scheduler = Scheduler(self)

        self.inprogress = set()

    def check_empty(self, response):
        if not self.running:
            self._closewait.callback('......')

    def _next_request(self):
        while self.start_requests:
            try:
                request = next(self.start_requests)
            except StopIteration:
                self.start_requests = None
            else:
                self.scheduler.enqueue_request(request)

        while len(self.inprogress) < 5 and self.scheduler.size() > 0:  # 最大并发数为5

            request = self.scheduler.next_request()
            if not request:
                break

            self.inprogress.add(request)
            d = getPage(bytes(request.url, encoding='utf-8'))
            d.addBoth(self._handle_downloader_output, request)
            d.addBoth(lambda x, req: self.inprogress.remove(req), request)
            d.addBoth(lambda x: self._next_request())

        if len(self.inprogress) == 0 and self.scheduler.size() == 0:
            self._closewait.callback(None)

    def _handle_downloader_output(self, body, request):
        """
        获取内容，执行回调函数，并且把回调函数中的返回值获取，并添加到队列中
        :param response: 
        :param request: 
        :return: 
        """
        import types

        response = Response(body, request)
        func = request.callback or self.spider.parse
        gen = func(response)
        if isinstance(gen, types.GeneratorType):
            for req in gen:
                self.scheduler.enqueue_request(req)

    @defer.inlineCallbacks
    def start(self):
        self._closewait = defer.Deferred()
        yield self._closewait

    def open_spider(self, spider, start_requests):
        self.start_requests = start_requests
        self.spider = spider
        reactor.callLater(0, self._next_request)


class Crawler(object):
    def __init__(self, spidercls):
        self.spidercls = spidercls

        self.spider = None
        self.engine = None

    @defer.inlineCallbacks
    def crawl(self):
        self.engine = ExecutionEngine()
        self.spider = self.spidercls()
        start_requests = iter(self.spider.start_requests())
        start_requests = iter(start_requests)
        self.engine.open_spider(self.spider, start_requests)
        yield self.engine.start()


class CrawlerProcess(object):
    def __init__(self):
        self._active = set()
        self.crawlers = set()

    def crawl(self, spidercls, *args, **kwargs):
        crawler = Crawler(spidercls)

        self.crawlers.add(crawler)
        d = crawler.crawl(*args, **kwargs)
        self._active.add(d)
        return d

    def start(self):
        dl = defer.DeferredList(self._active)
        dl.addBoth(self._stop_reactor)
        reactor.run()

    def _stop_reactor(self, _=None):
        reactor.stop()


class Spider(object):
    def start_requests(self):
        for url in self.start_urls:
            yield Request(url)


class ChoutiSpider(Spider):
    name = "chouti"
    start_urls = [
        'http://dig.chouti.com/',
    ]

    def parse(self, response):
        print(response.text)


class CnblogsSpider(Spider):
    name = "cnblogs"
    start_urls = [
        'http://www.cnblogs.com/',
    ]

    def parse(self, response):
        print(response.text)


if __name__ == '__main__':

    spider_cls_list = [ChoutiSpider, CnblogsSpider]

    crawler_process = CrawlerProcess()
    for spider_cls in spider_cls_list:
        crawler_process.crawl(spider_cls)

    crawler_process.start()

import types
from twisted.internet import defer
from twisted.web.client import getPage
from twisted.internet import reactor



class Request(object):
    def __init__(self, url, callback):
        self.url = url
        self.callback = callback
        self.priority = 0


class HttpResponse(object):
    def __init__(self, content, request):
        self.content = content
        self.request = request


class ChouTiSpider(object):

    def start_requests(self):
        url_list = ['http://www.cnblogs.com/', 'http://www.bing.com']
        for url in url_list:
            yield Request(url=url, callback=self.parse)

    def parse(self, response):
        print(response.request.url)
        # yield Request(url="http://www.baidu.com", callback=self.parse)




from queue import Queue
Q = Queue()


class CallLaterOnce(object):
    def __init__(self, func, *a, **kw):
        self._func = func
        self._a = a
        self._kw = kw
        self._call = None

    def schedule(self, delay=0):
        if self._call is None:
            self._call = reactor.callLater(delay, self)

    def cancel(self):
        if self._call:
            self._call.cancel()

    def __call__(self):
        self._call = None
        return self._func(*self._a, **self._kw)


class Engine(object):
    def __init__(self):
        self.nextcall = None
        self.crawlling = []
        self.max = 5
        self._closewait = None

    def get_response(self,content, request):
        response = HttpResponse(content, request)
        gen = request.callback(response)
        if isinstance(gen, types.GeneratorType):
            for req in gen:
                req.priority = request.priority + 1
                Q.put(req)


    def rm_crawlling(self,response,d):
        self.crawlling.remove(d)

    def _next_request(self,spider):
        if Q.qsize() == 0 and len(self.crawlling) == 0:
            self._closewait.callback(None)

        if len(self.crawlling) >= 5:
            return
        while len(self.crawlling) < 5:
            try:
                req = Q.get(block=False)
            except Exception as e:
                req = None
            if not req:
                return
            d = getPage(req.url.encode('utf-8'))
            self.crawlling.append(d)
            d.addCallback(self.get_response, req)
            d.addCallback(self.rm_crawlling,d)
            d.addCallback(lambda _: self.nextcall.schedule())


    @defer.inlineCallbacks
    def crawl(self):
        spider = ChouTiSpider()
        start_requests = iter(spider.start_requests())
        flag = True
        while flag:
            try:
                req = next(start_requests)
                Q.put(req)
            except StopIteration as e:
                flag = False

        self.nextcall = CallLaterOnce(self._next_request,spider)
        self.nextcall.schedule()

        self._closewait = defer.Deferred()
        yield self._closewait

    @defer.inlineCallbacks
    def pp(self):
        yield self.crawl()

_active = set()
obj = Engine()
d = obj.crawl()
_active.add(d)

li = defer.DeferredList(_active)
li.addBoth(lambda _,*a,**kw: reactor.stop())

reactor.run()

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14、源码阅读

 更多文档参见：http://scrapy-chs.readthedocs.io/zh_CN/latest/index.html

文章转载自https://www.cnblogs.com/wupeiqi/articles/6229292.html