python正則爬蟲無響應

import requests
import re

content = requests.get('https://book.douban.com/').text
pattern=re.compile('<li.*?"cover".*?href=(.*?)title=(.*?).*"author">(.*?)</div>.*"year">(.*?)</span></li>',re.S)
results = re.findall(pattern, content)
for result in results:
    url, name, author, date = result
    author = re.sub('\s', '', author)
    date = re.sub('\s', '', date)
    print(url, name, author, date)

無響應，大家能告訴我什么原因嗎？謝謝啦。