python网络爬虫与信息提取 学习笔记day3

Day3：

只需两行代码解析html或xml信息    具体代码实现:day3_1    注意BeautifulSoup的B和S需要大写，因为python大小写敏感

 

import requests
r= requests.get("http://python123.io/ws/demo.html")
r.text
demo = r.text
from bs4 import BeautifulSoup
soup = BeautifulSoup(demo , "html.parser")
print(soup.prettify())

　　

BeautifulSoup库的基本元素：详参html的基本信息

 

 

from bs4 import BeautifulSoup        语句含义：从bs4库中引入一个BeautifulSoup的类型

下行遍历，上行遍历和平行遍历：

 

 

 

 爬取中国大学排名

import requests
from bs4 import BeautifulSoup
import bs4def getHTMLText(url):try:r = requests.get(url, timeout=30)r.raise_for_status()r.encoding = r.apparent_encodingreturn r.textexcept:return ""def fillUnivList(ulist, html):soup = BeautifulSoup(html, "html.parser")for tr in soup.find('tbody').children:if isinstance(tr, bs4.element.Tag):tds = tr('td')ulist.append([tds[0].string, tds[1].string, tds[3].string])def printUnivList(ulist, num):print("{:^10}\t{:^6}\t{:^10}".format("排名","学校名称","总分"))for i in range(num):u=ulist[i]print("{:^10}\t{:^6}\t{:^10}".format(u[0],u[1],u[2]))def main():uinfo = []url = 'http://www.zuihaodaxue.cn/zuihaodaxuepaiming2016.html'html = getHTMLText(url)fillUnivList(uinfo, html)printUnivList(uinfo, 20) # 20 univs
main()