求个大神解救一下小白（关于爬虫的问题）

from urllib.request import urlopen
from bs4 import BeautifulSoup
import re
html = urlopen("http://www.baidu.com")
bsObj = BeautifulSoup(html,"html5lib")
for link in bsObj.findAll("a",href=re.compile("baidu")):
print(link.attrs['href'])
print(len(bsObj.findAll("a")))
获取不到网页所有a标签下的url，求大神指点一二