python--图片下载

#coding:utf-8
import urllib.request
url=input("url ")
up=urllib.request.urlopen(url)
s=up.read()
h="<img style"
c=".jpg"
temp=""
posh=-len(h)
posc=-len(c)
i=0
while i<s.count(h):
    posh=s.find(h,posc+len(h))
    posc=s.find(c,posh+len(h))
    t=s[posh:posc+len(c)]
    http=t.find("http")
    #if len(t[http:])==len(temp):
    url=t[http:]
    urllib.request.urlretrieve(url,str(i)+".jpg")
    i+=1