python中with open写入错误

import urllib.request
url = 'http://www.csdn.net'
response = urllib.request.urlopen(url)
print(str(response.read()))
with open('E:\Python文件\爬虫\CSDN.html\csdnhtml.html','w') as f:
    f.write(str(response.read()))

问题：为什么会写入“  b''  ”?不应该写入csdn的html源代码吗？怎么处理？

import requests

url = 'http://www.csdn.net'

r = requests.get(url)

with open('E:\Python文件\爬虫\CSDN.html\csdnhtml.html','w',encoding='utf-8') as f:

    f.write(r.text)

response.read()返回的是 bytes 类型数据吧，是不是要转换一下再存储？参考https://blog.csdn.net/chengqiuming/article/details/85931725

我也没怎么用过urlopen，不是很清楚