Scrapy框架的八个扩展-白红宇

Scrapy框架的八个扩展

阅读量：6713 次

发布时间：2019-06-25

本文共 11684 字，大约阅读时间需要 38 分钟。

一、proxies代理

首先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/}

缺点：原生代理是把代理放在python环境变量里面，也就是要依赖于python环境变量，要用的时候然后再去变量里面搜索，一个个分割字符进行匹配，效率低，low。

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,}

自定义proxies

二、Https证书

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

自定义Https证书

三、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 HttpCacheMiddlewarefrom scrapy.extensions.httpcache import DummyPolicyfrom 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'

缓存

四、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,# }

下载中间件

五、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.htmlSPIDER_MIDDLEWARES = {   # 'step8_king.middlewares.SpiderMiddleware': 543,}

爬虫中间件

六、pipelines扩展

from scrapy.exceptions import DropItemclass CustomPipeline(object):    def __init__(self,v):        self.value = v    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()    @classmethod    def from_crawler(cls, crawler):        """        初始化时候，用于创建pipeline对象        :param crawler:         :return:         """        val = crawler.settings.getint('MMMM')        return cls(val)    def open_spider(self,spider):        """        爬虫开始执行时，调用        :param spider:         :return:         """        print('000000')    def close_spider(self,spider):        """        爬虫关闭时，被调用        :param spider:         :return:         """        print('111111')自定义pipeline

pipelines扩展

七、exception信号量处理

from scrapy import signalsclass MyExtension(object):    def __init__(self, value):        self.value = value    @classmethod    def from_crawler(cls, crawler):        val = crawler.settings.getint('MMMM')        ext = cls(val)        crawler.signals.connect(ext.spider_opened, signal=signals.spider_opened)        crawler.signals.connect(ext.spider_closed, signal=signals.spider_closed)        return ext    def spider_opened(self, spider):        print('open')    def spider_closed(self, spider):        print('close')

extension信号量处理

八、url的去重

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)自定义URL去重操作

url去重

小扩展，关于Scrapy默认的URL去重，只是简单的把URL加到集合set()里面，此外还有另一种更好的去重方法，是Scrapy_Redis中使用的，具体步骤为：

- 使用sha1加密request得到指纹

- 把指纹存在redis的集合中

- 下一次新来一个request，同样的方式生成指纹，判断指纹是否存在reids的集合中

实现的代码

fp = hashlib.sha1()fp.update(to_bytes(request.method))  #请求方法fp.update(to_bytes(canonicalize_url(request.url))) #urlfp.update(request.body or b'')  #请求体return fp.hexdigest()

added = self.server.sadd(self.key, fp)return added != 0

转载于:https://www.cnblogs.com/linyuhong/p/10171003.html

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