import urllib.request
response = urllib.request.urlopen(‘http://www.placekitten.com/g/500/600‘)
cat_img = response.read()

with open(‘cat_500_600.jpg‘,‘wb‘) as f:
    f.write(cat_img)

urlopen()括号里既可以是一个字符串也可以是一个request对象，当传入字符串的时候会转换成一个request对象，因此代码

response = urllib.request.urlopen(‘http://www.placekitten.com/g/500/600‘)  也可以写成

1. req = urllib.request.Request(‘http://www.placekitten.com/g/500/600‘)
2. response = urllib.request.urlopen(req)

         responce还有geturl,info,getcode方法

代码with open(‘cat_500_600.jpg‘,‘wb‘) as f:

       f.write(cat_img)等价于

1. f = open(‘cat_500_600.jpg‘,‘wb‘) 
2. try:  
3.     data =  f.write(cat_img)
4. finally:  
5.     f.close() 

python下载图片