知乎信息爬取（存在bug，望大牛指点）

import requests
from lxml import etree
import pymysql

class MysqlHelper(object):
    def __init__(self):
        self.db = pymysql.connect(host='127.0.0.1', port=3306, user='root', password='123456', database='py11', charset='utf8')
        self.cursor = self.db.cursor()

    def execute_modify_sql(self,sql, data):
        self.cursor.execute(sql, data)
        self.db.commit()

    def __del__(self):
        self.cursor.close()
        self.db.close()

if __name__ == '__main__':
    conn = MysqlHelper()
    conn.execute_modify_sql('insert into zhihu(title) VALUE (%s)', data=('hehehe'))

base_url = 'https://www.zhihu.com/people/leedaye/answers?page=%s'
headers = {
        "User-Agent": 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:41.0) Gecko/20100101 Firefox/41.0',
        "Referer": "http://www.zhihu.com/",
        'Host': 'www.zhihu.com',
}
myhelper = MysqlHelper()
sql = 'INSERT INTO zhihu(title,tet) VALUES' \
      ' (%s, %s)'

for i in range(1,21):
    url = base_url % i
    response = requests.get(url,headers=headers)
    html_ele = etree.HTML(response.text)
    li_list = html_ele.xpath('//*[@id="Profile-answers"]/div[2]')
    for li_ele in li_list:
        title = li_ele.xpath('./div[1]/div/h2/div/a')[0].text
        print(title)
        tet = li_ele.xpath('./div[1]/div/div[2]/div[1]/span')[0].text
        data = (title,tet)
        myhelper.execute_modify_sql(sql, data)