为什么会报这个问题：AttributeError: 'Request' object has no attribute 'addheader'
from urllib import request
import urllib.request
url="http://www.baidu.com";
print("第一种方法");
req=request.Request(url);
req.addheader("user-agent","Mozilla/5.0");
response=request.urlopen(req);
print(response.getcode());
print(len(response.read()));
