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 bs4
 
def getHTMLText(url):
    try:
        r = requests.get(url, timeout=30)
        r.raise_for_status()
        r.encoding = r.apparent_encoding
        return r.text
    except:
        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}	{:^6}	{:^10}".format("排名","学校名称","总分"))
    for i in range(num):
        u=ulist[i]
        print("{:^10}	{:^6}	{:^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()