python scrapy框架爬取知乎动态页面

说明：纯文科生。2个月正式的python代码经验。

目的：用scrapy框架爬取知乎的这个页面：https://www.zhihu.com/search?type=content&q=%E6%9C%BA%E5%99%A8%E5%AD%A6%E4%B9%A0
红框框里面的内容

步骤：
一、创建project：cd到要创建项目的目录，执行以下命令。

scrapy startproject zhihuSpider

二、创建spider：cd到spiders文件夹，执行以下命令，ZH是你爬虫的名字，必须唯一；zhihu.com是allowed_domains。

$ scrapy genspider ZH zhihu.com

三、item.py，收集的数据分别有问题的内容、回答者的姓名和自我介绍、答案内容。

# -*- coding: utf-8 -*-# Define here the models for your scraped items# See documentation in:# http://doc.scrapy.org/en/latest/topics/items.htmlimport scrapy# 关于每一个问题的信息class QuesInfoItem(scrapy.Item):question = scrapy.Field() #问题内容author_name = scrapy.Field() #作者姓名author_bio = scrapy.Field() #作者简介answer_content = scrapy.Field() #答案

四、middlewares.py，导入time模块，记录爬虫耗时

# -*- coding: utf-8 -*-# Define here the models for your spider middleware# See documentation in:# http://doc.scrapy.org/en/latest/topics/spider-middleware.htmlfrom scrapy import signalsimport time,osclass ZhihuSpiderMiddleware(object):    # Not all methods need to be defined. If a method is not defined,    # scrapy acts as if the spider middleware does not modify the    # passed objects.    @classmethod    def from_crawler(cls, crawler):        # This method is used by Scrapy to create your spiders.        s = cls()        crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)        crawler.signals.connect(s.spider_closed, signal=signals.spider_closed)        return s    def process_spider_input(self, response, spider):        # Called for each response that goes through the spider        # middleware and into the spider.        # Should return None or raise an exception.        return None    def process_spider_output(self, response, result, spider):        # Called with the results returned from the Spider, after        # it has processed the response.        # Must return an iterable of Request, dict or Item objects.        for i in result:            yield i    def process_spider_exception(self, response, exception, spider):        # Called when a spider or process_spider_input() method        # (from other spider middleware) raises an exception.        # Should return either None or an iterable of Response, dict        # or Item objects.        pass    def process_start_requests(self, start_requests, spider):        # Called with the start requests of the spider, and works        # similarly to the process_spider_output() method, except        # that it doesn’t have a response associated.        # Must return only requests (not items).        for r in start_requests:            yield r    def spider_opened(self, spider):        self.startTime = time.time()        # print('__file__ is %s' % __file__)        # print ("path ====== %s " % os.path.normcase(__file__))        print('   爬虫开始   '.center(50, "*"))        print(('   开始时间：%.2f   ' % self.startTime).center(50, "*"))    def spider_closed(self, spider):        self.endTime = time.time()        _t = self.endTime - self.startTime        print(('   结束时间：%.2f   ' % self.endTime).center(50, "*"))        print(('   耗时：%.2f s   ' % _t).center(50, "*"))        print('   爬虫结束   '.center(50, "*"))class MyproxiesSpiderMiddleware(object):    def __init__(self):          self.ips = []            def process_request(self, request, spider):          pass        # if spider.name == 'question':        #     ip = "https://116.3.94.128:80"        #     # print("============ 使用代理 %s ============" % ip)        #     request.meta["proxy"] = ip

五、piplines.py，添加 ZhihuSpiderWriteToCSVPipeline 和 ZhihuSpiderWriteToDBPipeline 类，将抓取的数据保存到csv文件和数据库当中

# -*- coding: utf-8 -*-# Define your item pipelines here# Don't forget to add your pipeline to the ITEM_PIPELINES setting# See: http://doc.scrapy.org/en/latest/topics/item-pipeline.htmlimport csvimport os,sysimport sqlite3from ZhihuSpider.items import QuesInfoItem#数据写入csv文件class ZhihuSpiderWriteToCSVPipeline(object):    def open_spider(self, spider):        # print("abs path is %s" %(os.path.abspath(sys.argv[0])))                self.csvFile = open(os.path.abspath('C:/Users/Administrator/Desktop/ZhihuSpider/test.csv'), "w+",newline='')        try:            self.write = csv.writer(self.csvFile)            self.write.writerow(('question', 'author_name', 'author_bio', 'answer_content'))        except Exception as e:            pass     def close_spider(self, spider):        self.csvFile.close()    def process_item(self, item, spider):        try:            self.write.writerow((item["question"], item["author_name"], item["author_bio"], item["answer_content"]))        except BaseException as e:            pass                    return item#数据写入数据库文件class ZhihuSpiderWriteToDBPipeline(object):    def open_spider(self, spider):        try:            self.conn = sqlite3.connect(os.path.abspath('C:/Users/Administrator/Desktop/ZhihuSpider/test.db'))            self.cursor = self.conn.cursor()        except BaseException as e:            pass                def close_spider(self, spider):        try:            self.cursor.close()            self.conn.commit()            self.conn.close()        except BaseException as e:            pass    def process_item(self, item, spider):        try:            if isinstance(item, QuesInfoItem):                self.cursor.execute('insert into question (question, author_name, author_bio, answer_content) values (?, ?, ?, ?)', (item["question"], item["author_name"], item["author_bio"], item["answer_content"]))        except BaseException as e:            print(e)            pass                    return item

六、setting.py，激活各个环节

# -*- coding: utf-8 -*-# Scrapy settings for zhihuSpider 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.htmlBOT_NAME = 'zhihuSpider'LOG_LEVEL= 'WARNING'SPIDER_MODULES = ['zhihuSpider.spiders']NEWSPIDER_MODULE = 'zhihuSpider.spiders'# Crawl responsibly by identifying yourself (and your website) on the user-agent#USER_AGENT = 'zhihuSpider (+http://www.yourdomain.com)'# Obey robots.txt rulesROBOTSTXT_OBEY = True# Configure maximum concurrent requests performed by Scrapy (default: 16)#CONCURRENT_REQUESTS = 32# 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#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': 'zh-cn',  'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36'}# Enable or disable spider middlewares# See http://scrapy.readthedocs.org/en/latest/topics/spider-middleware.htmlSPIDER_MIDDLEWARES = {   'zhihuSpider.middlewares.ZhihuspiderSpiderMiddleware': 543,}# Enable or disable downloader middlewares# See http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.htmlDOWNLOADER_MIDDLEWARES = {   'zhihuSpider.middlewares.MyproxiesSpiderMiddleware': 544,}DOWNLOAD_DELAY = 1# Enable or disable extensions# See http://scrapy.readthedocs.org/en/latest/topics/extensions.html#EXTENSIONS = {#    'scrapy.extensions.telnet.TelnetConsole': None,#}# Configure item pipelines# See http://scrapy.readthedocs.org/en/latest/topics/item-pipeline.htmlITEM_PIPELINES = {   'zhihuSpider.pipelines.ZhihuspiderWriteToCSVPipeline': 300,  # ZhihuspiderWriteToCSVPipeline 与 pipelines 中 class 名称相同   'zhihuSpider.pipelines.ZhihuspiderWriteToDBPipeline': 400  # ZhihuspiderWriteToDBPipeline 与 pipelines 中 class 名称相同}# Enable and configure the AutoThrottle extension (disabled by default)# See http://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 http://scrapy.readthedocs.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'

七、重头的ZH.py
1）代码：

# -*- coding: utf-8 -*-import scrapy#import requestsfrom scrapy import Requestfrom scrapy.spiders import CrawlSpiderimport timeimport reimport jsonfrom ZhihuSpider.items import QuesInfoItemclass ZhSpider(CrawlSpider):    name = 'ZH'    allowed_domains = ['zhihu.com']    # start_urls是Spider在启动时进行爬取的入口URL列表。第一个被获取到的页面的URL将是其中一个，    # 后续的URL从初始的URL的响应中获取    start_urls = ['https://www.zhihu.com/r/search?q=%E6%9C%BA%E5%99%A8%E5%AD%A6%E4%B9%A0',    'https://www.zhihu.com/r/search?q=%E6%9C%BA%E5%99%A8%E5%AD%A6%E4%B9%A0&correction=1&type=content&offset=30',    ]    i = 0    # parse是Spider的一个方法。被调用时，每个初始的URL响应后返回的response对象，将会作为唯一的参数返回给该方法    # 该方法负责解析返回的数据（respose data）、提取数据（item）以及生成需要进一步处理的URL的Response对象    def parse(self, response):        # print('***********************\n',response.body,'***********************\n\n')        print('*************开始下载json文件:*********************')        # 1、实现网页的解析，生成item        # 首先打开js路径，获取'htmls'KEY下面的内容，是一个整体的str文件，没有标KEY，所以用re去解析它        try:            # print(type(response.body))            # print(type(response.text))            jsDict = json.loads(response.body)            # print(type(jsDict))            print('*************开始解析页面*********************')            questions = jsDict['htmls']                # 抽取所有的问题和对应的follwer_num, answer_num和answer_abstract            for q in questions:                item = QuesInfoItem()                # 删去源代码中关键词“<em>机器学习</em>”的标签                q = q.replace('<em>','').replace('</em>','')                # 问题信息在标签 class=\"js-title-link\">和</a>当中                question = re.findall('class=\"js-title-link\">(.*?)</a>',q)[0]                print(question)                item['question'] = question                time.sleep(2)                        # 作者姓名在标签 data-author-name=\"和\" data-entry-url=\"当中                try:                    author_name = re.findall('data-author-name=\"(.*?)\" data-entry-url=\"',q)[0]                    print('作者姓名:',author_name)                except:                    author_name = None                item['author_name'] = author_name                    # 作者简介在标签 <span title=\"和\" class=\"bio\">当中                try:                    author_bio = re.findall('<span title=\"(.*?)\" class=\"bio\">',q)                    print('作者简介:',author_bio)                except:                    author_bio = None                item['author_bio'] = author_bio                time.sleep(2)                # 回答内容信息在标签 <script type=\"text\" class=\"content\">和</script>当中                try:                    answer_content = re.findall('<script type=\"text\" class=\"content\">(.*?)</script>', q)[0]                    print(answer_content[:100]) #内容太多只打印一部分出来看一下                except:                    answer_content = None                item['answer_content'] = answer_content                time.sleep(2)                yield item            # 2、构造下一页的链接并回调给parse方法            first_url = 'https://www.zhihu.com/r/search?q=%E6%9C%BA%E5%99%A8%E5%AD%A6%E4%B9%A0'            # 下一页链接信息在js文件的['paging']标签下的['next']KEY中            nexturl = jsDict['paging']['next']            last_url = re.findall('&(.*)', nexturl)[0]            url = first_url + '&' +last_url            print(url)            yield Request(url, callback=self.parse)         except json.decoder.JSONDecodeError as e: #这个报错开始是因为找错了url一直报错加的，现在应该没关系可以去掉了            print('JSONDecodeError')

2）如何找到js的url：查看源代码发现要抽取的内容在<script></script>标签内，是 javascript 动态加载的，Firefox浏览器，F12打开web开发者工具—网络（network），点击页面中的“更多”，在新出现的URL中查看，发现这个链接的响应（response）符合条件。用json.loads()方法将response.body这一byte类型的文件转化为dict类型的文件。

3）如何解析网页：用正则表达式进行解析，只要定位好要抽取的内容的位置，利用（.*？）符号表示要抽取的信息内容。比如：问题信息在标签 class=\"js-title-link\">和</a>当中，所以 question = re.findall('class=\"js-title-link\">(.*?)</a>',q)[0]

4）如何构造下一页url：下一页链接信息在js文件的['paging']标签下的['next']KEY中，抽取并组合一下就好了。

代码链接：https://github.com/MTINGSUN/zhihuspider.git

以上。