Python爬虫包 BeautifulSoup 学习（三） 实例

一步一步构建一个爬虫实例，抓取糗事百科的段子

先不用beautifulsoup包来进行解析

第一步，访问网址并抓取源码

# -*- coding: utf-8 -*-# @Author: HaonanWu# @Date:   2016-12-22 16:16:08# @Last Modified by:   HaonanWu# @Last Modified time: 2016-12-22 20:17:13import urllibimport urllib2import reimport osif __name__ == '__main__':    # 访问网址并抓取源码    url = 'http://www.qiushibaike.com/textnew/page/1/?s=4941357'    user_agent = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.99 Safari/537.36'    headers = {'User-Agent':user_agent}    try:        request = urllib2.Request(url = url, headers = headers)        response = urllib2.urlopen(request)        content = response.read()    except urllib2.HTTPError as e:        print e        exit()    except urllib2.URLError as e:        print e        exit()    print content.decode('utf-8')

第二步，利用正则表达式提取信息
首先先观察源码中，你需要的内容的位置以及如何识别
然后用正则表达式去识别读取
注意正则表达式中的 . 是不能匹配\n的，所以需要设置一下匹配模式。

# -*- coding: utf-8 -*-# @Author: HaonanWu# @Date:   2016-12-22 16:16:08# @Last Modified by:   HaonanWu# @Last Modified time: 2016-12-22 20:17:13import urllibimport urllib2import reimport osif __name__ == '__main__':    # 访问网址并抓取源码    url = 'http://www.qiushibaike.com/textnew/page/1/?s=4941357'    user_agent = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.99 Safari/537.36'    headers = {'User-Agent':user_agent}    try:        request = urllib2.Request(url = url, headers = headers)        response = urllib2.urlopen(request)        content = response.read()    except urllib2.HTTPError as e:        print e        exit()    except urllib2.URLError as e:        print e        exit()    regex = re.compile('<div class="content">.*?<span>(.*?)</span>.*?</div>', re.S)    items = re.findall(regex, content)    # 提取数据    # 注意换行符，设置 . 能够匹配换行符    for item in items:        print item

第三步，修正数据并保存到文件中

# -*- coding: utf-8 -*-# @Author: HaonanWu# @Date:   2016-12-22 16:16:08# @Last Modified by:   HaonanWu# @Last Modified time: 2016-12-22 21:41:32import urllibimport urllib2import reimport osif __name__ == '__main__':    # 访问网址并抓取源码    url = 'http://www.qiushibaike.com/textnew/page/1/?s=4941357'    user_agent = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.99 Safari/537.36'    headers = {'User-Agent':user_agent}    try:        request = urllib2.Request(url = url, headers = headers)        response = urllib2.urlopen(request)        content = response.read()    except urllib2.HTTPError as e:        print e        exit()    except urllib2.URLError as e:        print e        exit()    regex = re.compile('<div class="content">.*?<span>(.*?)</span>.*?</div>', re.S)    items = re.findall(regex, content)    # 提取数据    # 注意换行符，设置 . 能够匹配换行符    path = './qiubai'    if not os.path.exists(path):        os.makedirs(path)    count = 1    for item in items:        #整理数据，去掉\n,将<br/>换成\n        item = item.replace('\n', '').replace('<br/>', '\n')        filepath = path + '/' + str(count) + '.txt'        f = open(filepath, 'w')        f.write(item)        f.close()        count += 1

第四步，将多个页面下的内容都抓取下来

# -*- coding: utf-8 -*-# @Author: HaonanWu# @Date:   2016-12-22 16:16:08# @Last Modified by:   HaonanWu# @Last Modified time: 2016-12-22 20:17:13import urllibimport urllib2import reimport osif __name__ == '__main__':    # 访问网址并抓取源码    path = './qiubai'    if not os.path.exists(path):        os.makedirs(path)    user_agent = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.99 Safari/537.36'    headers = {'User-Agent':user_agent}    regex = re.compile('<div class="content">.*?<span>(.*?)</span>.*?</div>', re.S)    count = 1    for cnt in range(1, 35):        print '第' + str(cnt) + '轮'        url = 'http://www.qiushibaike.com/textnew/page/' + str(cnt) + '/?s=4941357'        try:            request = urllib2.Request(url = url, headers = headers)            response = urllib2.urlopen(request)            content = response.read()        except urllib2.HTTPError as e:            print e            exit()        except urllib2.URLError as e:            print e            exit()        # print content        # 提取数据        # 注意换行符，设置 . 能够匹配换行符        items = re.findall(regex, content)        # 保存信息        for item in items:            #   print item            #整理数据，去掉\n,将<br/>换成\n            item = item.replace('\n', '').replace('<br/>', '\n')            filepath = path + '/' + str(count) + '.txt'            f = open(filepath, 'w')            f.write(item)            f.close()            count += 1    print '完成'

使用BeautifulSoup对源码进行解析

# -*- coding: utf-8 -*-# @Author: HaonanWu# @Date:   2016-12-22 16:16:08# @Last Modified by:   HaonanWu# @Last Modified time: 2016-12-22 21:34:02import urllibimport urllib2import reimport osfrom bs4 import BeautifulSoupif __name__ == '__main__':    url = 'http://www.qiushibaike.com/textnew/page/1/?s=4941357'    user_agent = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.99 Safari/537.36'    headers = {'User-Agent':user_agent}    request = urllib2.Request(url = url, headers = headers)    response = urllib2.urlopen(request)    # print response.read()    soup_packetpage = BeautifulSoup(response, 'lxml')    items = soup_packetpage.find_all("div", class_="content")    for item in items:        try:            content = item.span.string        except AttributeError as e:            print e            exit()        if content:            print content + "\n"

这是用BeautifulSoup去抓取书本以及其价格的代码
可以通过对比得出到bs4对标签的读取以及标签内容的读取
（因为我自己也没有学到这一部分，目前只能依葫芦画瓢地写）

# -*- coding: utf-8 -*-# @Author: HaonanWu# @Date:   2016-12-22 20:37:38# @Last Modified by:   HaonanWu# @Last Modified time: 2016-12-22 21:27:30import urllib2import urllibimport re  from bs4 import BeautifulSoup  url = "https://www.packtpub.com/all"try:    html = urllib2.urlopen(url)  except urllib2.HTTPError as e:    print e    exit()soup_packtpage = BeautifulSoup(html, 'lxml')  all_book_title = soup_packtpage.find_all("div", class_="book-block-title")  price_regexp = re.compile(u"\s+\$\s\d+\.\d+")  for book_title in all_book_title:      try:        print "Book's name is " + book_title.string.strip()    except AttributeError as e:        print e        exit()    book_price = book_title.find_next(text=price_regexp)      try:        print "Book's price is "+ book_price.strip()    except AttributeError as e:        print e        exit()    print ""