Scrapy框架

#1、执行全局命令：请确保不在某个项目的目录下，排除受该项目配置的影响 scrapy startproject MyProject

cd MyProject
scrapy genspider baidu www.baidu.com

scrapy settings --get XXX #如果切换到项目目录下，看到的则是该项目的配置  scrapy runspider baidu.py

scrapy shell https://www.baidu.com
    response
    response.status
    response.body
    view(response)
    
scrapy view https://www.taobao.com #如果页面显示内容不全，不全的内容则是ajax请求实现的，以此快速定位问题  scrapy fetch --nolog --headers https://www.taobao.com

scrapy version #scrapy的版本  scrapy version -v #依赖库的版本 #2、执行项目命令：切到项目目录下 scrapy crawl baidu
scrapy check
scrapy list
scrapy parse http://quotes.toscrape.com/ --callback parse
scrapy bench 

#在项目目录下新建：entrypoint.py from scrapy.cmdline import execute
execute([‘scrapy‘, ‘crawl‘, ‘xiaohua‘])

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

#1、name = ‘amazon‘  定义爬虫名，scrapy会根据该值定位爬虫程序
所以它必须要有且必须唯一（In Python 2 this must be ASCII only.） #2、allowed_domains = [‘www.amazon.cn‘]  定义允许爬取的域名，如果OffsiteMiddleware启动（默认就启动），
那么不属于该列表的域名及其子域名都不允许爬取
如果爬取的网址为：https://www.example.com/1.html，那就添加‘example.com‘到列表. #3、start_urls = [‘http://www.amazon.cn/‘] 如果没有指定url，就从该列表中读取url来生成第一个请求 #4、custom_settings 值为一个字典，定义一些配置信息，在运行爬虫程序时，这些配置会覆盖项目级别的配置
所以custom_settings必须被定义成一个类属性，由于settings会在类实例化前被加载 #5、settings 通过self.settings[‘配置项的名字‘]可以访问settings.py中的配置，如果自己定义了custom_settings还是以自己的为准 #6、logger 日志名默认为spider的名字
self.logger.debug(‘=============>%s‘ %self.settings[‘BOT_NAME‘]) #5、crawler：了解 该属性必须被定义到类方法from_crawler中 #6、from_crawler(crawler, *args, **kwargs)：了解 You probably won’t need to override this directly  because the default implementation acts as a proxy to the __init__() method, calling it with the given arguments args and named arguments kwargs. #7、start_requests() 该方法用来发起第一个Requests请求，且必须返回一个可迭代的对象。它在爬虫程序打开时就被Scrapy调用，Scrapy只调用它一次。
默认从start_urls里取出每个url来生成Request(url, dont_filter=True) #针对参数dont_filter,请看自定义去重规则  如果你想要改变起始爬取的Requests，你就需要覆盖这个方法，例如你想要起始发送一个POST请求，如下 class MySpider(scrapy.Spider):
    name = ‘myspider‘ def start_requests(self): return [scrapy.FormRequest("http://www.example.com/login",
                                   formdata={‘user‘: ‘john‘, ‘pass‘: ‘secret‘},
                                   callback=self.logged_in)] def logged_in(self, response): # here you would extract links to follow and return Requests for # each of them, with another callback pass #8、parse(response) 这是默认的回调函数，所有的回调函数必须返回an iterable of Request and/or dicts or Item objects. #9、log(message[, level, component])：了解 Wrapper that sends a log message through the Spider’s logger, kept for backwards compatibility. For more information see Logging from Spiders. #10、closed(reason) 爬虫程序结束时自动触发

去重规则应该多个爬虫共享的，但凡一个爬虫爬取了，其他都不要爬了，实现方式如下 #方法一： 1、新增类属性
visited=set() #类属性 2、回调函数parse方法内： def parse(self, response): if response.url in self.visited: return None
    .......

    self.visited.add(response.url) #方法一改进：针对url可能过长，所以我们存放url的hash值 def parse(self, response):
        url=md5(response.request.url) if url in self.visited: return None
    .......

    self.visited.add(url) #方法二：Scrapy自带去重功能 配置文件：
DUPEFILTER_CLASS = ‘scrapy.dupefilter.RFPDupeFilter‘ #默认的去重规则帮我们去重，去重规则在内存中 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，去重规则放文件中  scrapy自带去重规则默认为RFPDupeFilter，只需要我们指定
Request(...,dont_filter=False) ，如果dont_filter=True则告诉Scrapy这个URL不参与去重。 #方法三： 我们也可以仿照RFPDupeFilter自定义去重规则， from scrapy.dupefilter import RFPDupeFilter，看源码，仿照BaseDupeFilter #步骤一：在项目目录下自定义去重文件dup.py class UrlFilter(object): def __init__(self):
        self.visited = set() #或者放到数据库  @classmethod def from_settings(cls, settings): return cls() def request_seen(self, request): if request.url in self.visited: return True
        self.visited.add(request.url) def open(self): # can return deferred pass def close(self, reason): # can return a deferred pass def log(self, request, spider): # log that a request has been filtered pass #步骤二：配置文件settings.py： DUPEFILTER_CLASS = ‘项目名.dup.UrlFilter‘ # 源码分析： from scrapy.core.scheduler import Scheduler
见Scheduler下的enqueue_request方法：self.df.request_seen(request)

#例一： import scrapy class MySpider(scrapy.Spider):
    name = ‘example.com‘ allowed_domains = [‘example.com‘]
    start_urls = [ ‘http://www.example.com/1.html‘, ‘http://www.example.com/2.html‘, ‘http://www.example.com/3.html‘,
    ] def parse(self, response):
        self.logger.info(‘A response from %s just arrived!‘, response.url) #例二：一个回调函数返回多个Requests和Items import scrapy class MySpider(scrapy.Spider):
    name = ‘example.com‘ allowed_domains = [‘example.com‘]
    start_urls = [ ‘http://www.example.com/1.html‘, ‘http://www.example.com/2.html‘, ‘http://www.example.com/3.html‘,
    ] def parse(self, response): for h3 in response.xpath(‘//h3‘).extract(): yield {"title": h3} for url in response.xpath(‘//a/@href‘).extract(): yield scrapy.Request(url, callback=self.parse) #例三：在start_requests()内直接指定起始爬取的urls，start_urls就没有用了， import scrapy from myproject.items import MyItem class MySpider(scrapy.Spider):
    name = ‘example.com‘ allowed_domains = [‘example.com‘] def start_requests(self): yield scrapy.Request(‘http://www.example.com/1.html‘, self.parse) yield scrapy.Request(‘http://www.example.com/2.html‘, self.parse) yield scrapy.Request(‘http://www.example.com/3.html‘, self.parse) def parse(self, response): for h3 in response.xpath(‘//h3‘).extract(): yield MyItem(title=h3) for url in response.xpath(‘//a/@href‘).extract(): yield scrapy.Request(url, callback=self.parse)

我们可能需要在命令行为爬虫程序传递参数，比如传递初始的url，像这样 #命令行执行 scrapy crawl myspider -a category=electronics #在__init__方法中可以接收外部传进来的参数 import scrapy class MySpider(scrapy.Spider):
    name = ‘myspider‘ def __init__(self, category=None, *args, **kwargs):
        super(MySpider, self).__init__(*args, **kwargs)
        self.start_urls = [‘http://www.example.com/categories/%s‘ % category] #... #注意接收的参数全都是字符串，如果想要结构化的数据，你需要用类似json.loads的方法

response.selector.css()
response.selector.xpath()
可简写为
response.css()
response.xpath() #1 //与/ response.xpath(‘//body/a/‘)# response.css(‘div a::text‘) >>> response.xpath(‘//body/a‘) #开头的//代表从整篇文档中寻找,body之后的/代表body的儿子 [] >>> response.xpath(‘//body//a‘) #开头的//代表从整篇文档中寻找,body之后的//代表body的子子孙孙 [<Selector xpath=‘//body//a‘ data=‘<a href="image1.html">Name: My image 1 <‘>, <Selector xpath=‘//body//a‘ data=‘<a href="image2.html">Name: My image 2 <‘>, <Selector xpath=‘//body//a‘ data=‘<a href=" image3.html">Name: My image 3 <‘>, <Selector xpath=‘//body//a‘ data=‘<a href="image4.html">Name: My image 4 <‘>, <Selector xpath=‘//body//a‘ data=‘<a href="image5.html">Name: My image 5 <‘>] #2 text >>> response.xpath(‘//body//a/text()‘) >>> response.css(‘body a::text‘) #3、extract与extract_first:从selector对象中解出内容 >>> response.xpath(‘//div/a/text()‘).extract()
[‘Name: My image 1 ‘, ‘Name: My image 2 ‘, ‘Name: My image 3 ‘, ‘Name: My image 4 ‘, ‘Name: My image 5 ‘] >>> response.css(‘div a::text‘).extract()
[‘Name: My image 1 ‘, ‘Name: My image 2 ‘, ‘Name: My image 3 ‘, ‘Name: My image 4 ‘, ‘Name: My image 5 ‘] >>> response.xpath(‘//div/a/text()‘).extract_first() ‘Name: My image 1 ‘ >>> response.css(‘div a::text‘).extract_first() ‘Name: My image 1 ‘ #4、属性：xpath的属性加前缀@ >>> response.xpath(‘//div/a/@href‘).extract_first() ‘image1.html‘ >>> response.css(‘div a::attr(href)‘).extract_first() ‘image1.html‘ #4、嵌套查找 >>> response.xpath(‘//div‘).css(‘a‘).xpath(‘@href‘).extract_first() ‘image1.html‘ #5、设置默认值 >>> response.xpath(‘//div[@id="xxx"]‘).extract_first(default="not found") ‘not found‘ #4、按照属性查找 response.xpath(‘//div[@id="images"]/a[@href="image3.html"]/text()‘).extract()
response.css(‘#images a[@href="image3.html"]/text()‘).extract() #5、按照属性模糊查找 response.xpath(‘//a[contains(@href,"image")]/@href‘).extract()
response.css(‘a[href*="image"]::attr(href)‘).extract()

response.xpath(‘//a[contains(@href,"image")]/img/@src‘).extract()
response.css(‘a[href*="imag"] img::attr(src)‘).extract()

response.xpath(‘//*[@href="image1.html"]‘)
response.css(‘*[href="image1.html"]‘) #6、正则表达式 response.xpath(‘//a/text()‘).re(r‘Name: (.*)‘)
response.xpath(‘//a/text()‘).re_first(r‘Name: (.*)‘) #7、xpath相对路径 >>> res=response.xpath(‘//a[contains(@href,"3")]‘)[0] >>> res.xpath(‘img‘)
[<Selector xpath=‘img‘ data=‘<img src="image3_thumb.jpg">‘>] >>> res.xpath(‘./img‘)
[<Selector xpath=‘./img‘ data=‘<img src="image3_thumb.jpg">‘>] >>> res.xpath(‘.//img‘)
[<Selector xpath=‘.//img‘ data=‘<img src="image3_thumb.jpg">‘>] >>> res.xpath(‘//img‘) #这就是从头开始扫描 [<Selector xpath=‘//img‘ data=‘<img src="image1_thumb.jpg">‘>, <Selector xpath=‘//img‘ data=‘<img src="image2_thumb.jpg">‘>, <Selector xpath=‘//img‘ data=‘<img src="image3_thumb.jpg">‘>, <Selector xpa
th=‘//img‘ data=‘<img src="image4_thumb.jpg">‘>, <Selector xpath=‘//img‘ data=‘<img src="image5_thumb.jpg">‘>] #8、带变量的xpath >>> response.xpath(‘//div[@id=$xxx]/a/text()‘,xxx=‘images‘).extract_first() ‘Name: My image 1 ‘ >>> response.xpath(‘//div[count(a)=$yyy]/@id‘,yyy=5).extract_first() #求有5个a标签的div的id ‘images‘

#一：可以写多个Pipeline类 #1、如果优先级高的Pipeline的process_item返回一个值或者None，会自动传给下一个pipline的process_item, #2、如果只想让第一个Pipeline执行，那得让第一个pipline的process_item抛出异常raise DropItem() #3、可以用spider.name == ‘爬虫名‘ 来控制哪些爬虫用哪些pipeline  二：示范 from scrapy.exceptions import DropItem class CustomPipeline(object): def __init__(self,v):
        self.value = v

    @classmethod def from_crawler(cls, crawler): """ Scrapy会先通过getattr判断我们是否自定义了from_crawler,有则调它来完
        成实例化 """ val = crawler.settings.getint(‘MMMM‘) return cls(val) def open_spider(self,spider): """ 爬虫刚启动时执行一次 """ print(‘000000‘) def close_spider(self,spider): """ 爬虫关闭时执行一次 """ print(‘111111‘) def process_item(self, item, spider): # 操作并进行持久化 # return表示会被后续的pipeline继续处理 return item # 表示将item丢弃，不会被后续pipeline处理 # raise DropItem()

#1、settings.py HOST="127.0.0.1" PORT=27017 USER="root" PWD="123" DB="amazon" TABLE="goods" ITEM_PIPELINES = { ‘Amazon.pipelines.CustomPipeline‘: 200,
} #2、pipelines.py class CustomPipeline(object): def __init__(self,host,port,user,pwd,db,table):
        self.host=host
        self.port=port
        self.user=user
        self.pwd=pwd
        self.db=db
        self.table=table

    @classmethod def from_crawler(cls, crawler): """ Scrapy会先通过getattr判断我们是否自定义了from_crawler,有则调它来完
        成实例化 """ HOST = crawler.settings.get(‘HOST‘)
        PORT = crawler.settings.get(‘PORT‘)
        USER = crawler.settings.get(‘USER‘)
        PWD = crawler.settings.get(‘PWD‘)
        DB = crawler.settings.get(‘DB‘)
        TABLE = crawler.settings.get(‘TABLE‘) return cls(HOST,PORT,USER,PWD,DB,TABLE) def open_spider(self,spider): """ 爬虫刚启动时执行一次 """ self.client = MongoClient(‘mongodb://%s:%s@%s:%s‘ %(self.user,self.pwd,self.host,self.port)) def close_spider(self,spider): """ 爬虫关闭时执行一次 """ self.client.close() def process_item(self, item, spider): # 操作并进行持久化  self.client[self.db][self.table].save(dict(item))

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

#1、与middlewares.py同级目录下新建proxy_handle.py import requests def get_proxy(): return requests.get("http://127.0.0.1:5010/get/").text def delete_proxy(proxy):
    requests.get("http://127.0.0.1:5010/delete/?proxy={}".format(proxy)) #2、middlewares.py from Amazon.proxy_handle import get_proxy,delete_proxy 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 """ proxy="http://" + get_proxy()
        request.meta[‘download_timeout‘]=20 request.meta["proxy"] = proxy print(‘为%s 添加代理%s ‘ % (request.url, proxy),end=‘‘) print(‘元数据为‘,request.meta) 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(‘返回状态吗‘,response.status) 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 """ print(‘代理%s，访问%s出现异常:%s‘ %(request.meta[‘proxy‘],request.url,exception)) import time
        time.sleep(5)
        delete_proxy(request.meta[‘proxy‘].split("//")[-1])
        request.meta[‘proxy‘]=‘http://‘+get_proxy() return request

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

#1、在与settings同级目录下新建一个文件，文件名可以为extentions.py,内容如下 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‘) #2、配置生效 EXTENSIONS = { "Amazon.extentions.MyExtension":200 }

# -*- coding: utf-8 -*- # Scrapy settings for step8_king project #
# For simplicity, this file contains only settings considered important or # commonly used. You can find more settings consulting the documentation: #
# http://doc.scrapy.org/en/latest/topics/settings.html # http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html # http://scrapy.readthedocs.org/en/latest/topics/spider-middleware.html # 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)‘ # Obey robots.txt rules # 4. 禁止爬虫配置 # ROBOTSTXT_OBEY = False # Configure maximum concurrent requests performed by Scrapy (default: 16) # 5. 并发请求数 # 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 # 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 # COOKIES_DEBUG = True # 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,] # 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 # ITEM_PIPELINES = { # ‘step8_king.pipelines.JsonPipeline‘: 700, # ‘step8_king.pipelines.FilePipeline‘: 500, # } # 12. 自定义扩展，基于信号进行调用 # 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 # 表示上一次的延迟时间
    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, # }