python3用BeautifulSoup抓取a标签

# -*- coding:utf-8 -*-
#python 2.7
#XiaoDeng
#http://tieba.baidu.com/p/2460150866

from bs4 import BeautifulSoup
import urllib.request

html_doc = "http://tieba.baidu.com/p/2460150866"
req = urllib.request.Request(html_doc)
webpage = urllib.request.urlopen(req)
html = webpage.read()

soup = BeautifulSoup(html, 'html.parser')

#抓取class='app_icon_link'的a标签
img_src=soup.findAll("a",{'class':'app_icon_link'})   #抓取a标签
for img in img_src:
    img=img.findAll('img')
    for k in img:
        k=k.get('src')
        print(k)