在python3.x中使用BeautifulSoup稍有不同,请参照下面
import urllib.request
from bs4 import BeautifulSoup
url = input("Enter-")
html = urllib.request.urlopen(url)
soup = BeautifulSoup(html,'html.parser')
tags = soup('a')
#soup相当于建立一个dict()
for tag in tags: print(tag.get('href',None))