python爬虫（Xpath）

import requests 

from lxml import etree 

url = 'http://tieba.baidu.com/p/2166231880' 

header = {'User-Agent':'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36'} 

r = requests.get(url,headers=header).content 

s = etree.HTML(r)

a=s.xpath('//div/img/@src')

b=0

for i in a:
try:
with open('C:\\Users\Administrator\\Desktop\\Python\\实写爬虫\\图片\\'+i[-9:-4]+'.jpg','wb') as f:
print(i)
text=(requests.get(i,headers=header).content)
f.write(text)
b=b+1
except:
print('完毕')
break