python学习--抓取一个网页上图片

#!/bin/python
# download_pic.py
# download picture
import os
import sys
from urllib.request import urlopen

url = sys.argv[1]
page = urlopen(url)
#需要指定编码格式
html = str(page.read(),encoding='utf8')
page.close()

#create directory
if os.path.exists("./picture") == False:
    os.makedirs('./picture')
    os.chdir('./picture')

head = html.find('<img')
while head != -1:
    html = html[head:]
    http_idx = html.find('http')
    if http_idx == -1:
        break
    html = html[http_idx:]
    tail = html.find('"')
    url = html[:tail]

    print("url:", url)
    cmd = "wget {0}".format(url)
    os.system(cmd)
    print ("cmd:", cmd)
    #html = page2[tail:]
    head = html.find('<img')

 用法： python download_pic.py http://image.baidu.com/