Python写爬虫，得到了图片链接，怎样写入文件

img_req=urllib2.Request(Img_URL)
img_response=opener.open(img_req)
try:
     out=open('code','wb')
     #print img_response.read()
     out.write(img_response.read())
     out.flush()
     out.close()
     print 'get code success'
except IOError:
     print 'file wrong'