百度贴吧的内容的爬取，以一个NBA吧的实例，在python3.6上，IDE是pycharm，最新的正则。

import urllib
import re
from urllib import request
#处理页面标签类
class Tool:
    #去除img标签,7位长空格
    removeImg = re.compile('<img.*?>| {7}|')
    #删除超链接标签
    removeAddr = re.compile('<a.*?>|</a>')
    #把换行的标签换为\n
    replaceLine = re.compile('<tr>|<div>|</div>|</p>')
    #将表格制表<td>替换为\t
    replaceTD= re.compile('<td>')
    #把段落开头换为\n加空两格
    replacePara = re.compile('<p.*?>')
    #将换行符或双换行符替换为\n
    replaceBR = re.compile('<br><br>|<br>')
    #将其余标签剔除
    removeExtraTag = re.compile('<.*?>')
    def replace(self,x):
        x = re.sub(self.removeImg,"",x)
        x = re.sub(self.removeAddr,"",x)
        x = re.sub(self.replaceLine,"\n",x)
        x = re.sub(self.replaceTD,"\t",x)
        x = re.sub(self.replacePara,"\n    ",x)
        x = re.sub(self.replaceBR,"\n",x)
        x = re.sub(self.removeExtraTag,"",x)
        #strip()将前后多余内容删除
        return x.strip()
class BDTB:
    def __init__(self,baseUrl,seeLZ,floorTag):
        self.baseURL = baseUrl
        self.seeLZ = '?see_lz='+str(seeLZ)
        self.tool = Tool()
        self.file = None
        # 楼层标号，初始为1
        self.floor = 1
        # 默认的标题，如果没有成功获取到标题的话则会用这个标题
        self.defaultTitle = u"百度贴吧"
        # 是否写入楼分隔符的标记
        self.floorTag = floorTag
    def getPage(self,pageNum):
        try:
            url = self.baseURL+self.seeLZ+'&pn='+str(pageNum)
            request = urllib.request.Request(url)
            response = urllib.request.urlopen(request)
            #print(response.read().decode('utf-8'))
            content = response.read().decode('utf-8')
            return content

        except urllib.error.URLError as e:
            if hasattr(e, "reason"):
                print(u"连接百度贴吧失败,错误原因", e.reason)
                return None
    def getTitle(self, page):
        #print(page)
        pattern = re.compile('<h3 class="core_title_txt.*?>(.*?)</h3>', re.S)
        result = re.search(pattern, str(page))
        if result:
            #print(result.group(1))
            return result.group(1).strip()
        else:
            return None
    def getPageNum(self, indexPage):
        pattern = re.compile('<span class="red">(.*?)</span>', re.S)
        result = re.search(pattern, indexPage)
        if result:
            #print(result.group(1))
            return result.group(1).strip()
        else:
            return None
    def getContent(self, page):
        pattern = re.compile('<div id="post_content_.*?>(.*?)</div>', re.S)
        items = re.findall(pattern, page)
        floor = 1
        contents = []
        #items_res = list()
        for item in items:
            content ='\n'+self.tool.replace(item)+'\n'
            contents.append(content)
            #print(floor,u'楼-----------------------------------------------------\n')
            #items_res.append(self.tool.replace(item))
            #print(self.tool.replace(item))
            floor += 1
            return contents
    def write(self, contents):
        for item in contents:
            filename = 'tieba.txt'
            with open(filename, 'a') as file_object:
                if self.floorTag == '1':
                    # 楼之间的分隔符
                    floorLine = "\n" + str(
                        self.floor) + u"-----------------------------------------------------------------------------------------\n"
                    file_object.write(floorLine)
                file_object.write(str(item))
                self.floor += 1
    def start(self):
        indexPage = self.getPage(1)
        #print(indexPage)
        pageNum = self.getPageNum(indexPage)
        title = self.getTitle(indexPage)
        if pageNum ==None:
            print('URL已失效，请重试！！')
            return
        try:
            print("该帖子共有"+str(pageNum)+'页')
            for i in range(1,int(pageNum)+1):
                print('正在写入第'+str(i)+'页数据')
                page = self.getPage(i)
                contents = self.getContent(page)
                self.write(contents)
        except IOError as e:
            print("写入异常，原因" + e.message)
        finally:
            print("写入任务完成")





# batb = BDTB(baseURL, 1,1)
# print(batb.getPage(1))
# print(u'请输入帖子网址')
# baseurl  = input(u'请输入帖子网址:')
# seeLZ = input("是否只获取楼主发言，是输入1，否输入0\n")
# floorTag = input("是否写入楼层信息，是输入1，否输入0\n")
# bdtb = BDTB(baseurl, seeLZ)
# bdtb.start()
#baseURL = 'https://tieba.baidu.com/p/' + str(input(u'https://tieba.baidu.com/p/'))
baseURL = 'https://tieba.baidu.com/p/3138733512'
seeLZ = input("是否只获取楼主发言，是输入1，否输入0\n")
floorTag = input("是否写入楼层信息，是输入1，否输入0\n")
bdtb = BDTB(baseURL,seeLZ,floorTag)
bdtb.start()