这个程序有借鉴别人的代码：

# -*- coding:utf-8 -*-

import os
import codecs
import json
import urllib
import urllib.request
from lxml import etree

class Spider:
    def __init__(self):
        self.pages = int(input('请输入需要爬取的页数(请输入50的倍数数字):'))
        self.url = 'http://tieba.baidu.com/f?kw=%E6%95%B4%E5%AE%B9&ie=utf-8&pn='
        self.ua_header = {"User-Agent" : "Mozilla/5.0(compatible;MSIE 9.0;Windows NT 6.1; Trident/5.0;"}


    def tiebaSpider(self):
        for page in range(50, self.pages + 1, 50):
            url = 'http://tieba.baidu.com/f?kw=%E6%95%B4%E5%AE%B9&ie=utf-8&pn=' + str(page)
            # 并且获取页面所有帖子链接,
            links = self.loadPage(url)


    #读取页面内容
    def  loadPage(self, url):
        req = urllib.request.Request(url, headers=self.ua_header)
        html = urllib.request.urlopen(req).read().decode('utf8',errors='replace')

        #解析html 为 HTML
        selector = etree.HTML(html)
        # print(selector)
        links = selector.xpath('//div[@class="threadlist_lz clearfix"]/div/a/@href')

        for link in links:
            link = "http://tieba.baidu.com" + link
            self.loadImages(link)


    # 获取
    def loadImages(self, link):
        req = urllib.request.Request(link, headers= self.ua_header)
        html = urllib.request.urlopen(req).read().decode('utf8',errors='replace')

        selector = etree.HTML(html)

        #获取这个帖子里所有回复人，回复内容，和帖子标题
        title = selector.xpath('//div[@class="left_section"]//div/h1/text()')[0]
        # 获取每个内容块
        content_field = selector.xpath('//div[@class="l_post j_l_post l_post_bright  "]')
        reply = {}
        reply['reply_title'] = title


        for each_content in content_field:
            reply_info = json.loads(each_content.xpath('@data-field')[0])
            author = reply_info['author']['user_name']
            reply_time = reply_info['content']['date']
            content = each_content.xpath('div[@class="d_post_content_main"]/div/cc/div[starts-with(@id, "post_content") \
                                                and contains(@class,"d_post_content j_d_post_content  clearfix")]')
            reply['reply_author'] = author
            reply['reply_content_time'] = reply_time
            reply['reply_content'] = content[0].xpath('string(.)').replace(' ', '')
            self.writeImages(reply)



    #按帖子title来建立文件名
    def writeImages(self, reply):
        s_path = './Baidu/'
        if not os.path.isdir(s_path):
            os.mkdir(s_path)
        else:
            pass
        file = codecs.open(s_path + str(reply['reply_title']) + '.txt', 'a', encoding='utf-8')
        file.write(reply['reply_author'] + ":" + reply['reply_content'] + '\n')
        file.close()



Spider = Spider()
Spider.tiebaSpider()

效果图：

1501579580(1).jpg