直接上代码,简单粗暴

res = "background:#000 url(http://p3.yokacdn.com/pic/YOKA/2019-01-25/U464P1TS1548411340_54313.jpg) no-repeat center top"
regex = "url\(([\s\S]*?)\)"
res1 = re.search(regex, res).group(1)
print(res1)