python3 urllib 设置 Host header 无效问题

import urllib.request

headers = {  
    "User-Agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/93.0.4577.63 Safari/537.36",  
  "Host": ""  
}  
debug = True  
  
import traceback  
def g_post2(url, data, domain):  
    try:  
        headers['Host'] = domain  
        opener = urllib.request.build_opener()  
        opener.addheaders = [  
            ('User-Agent', headers['User-Agent']),  
  ('Host', domain)  
        ]  
  
        print(opener.addheaders)  
  
        return opener.open(url, data, timeout=2).read().decode()  
    except Exception as e:  
        print(e)  
        if debug:  
            traceback.print_exc()  
  
print(g_post2('http://httpbin.org/post','data'.encode(), 'qq.com'))

输出的结果看设置的 UA 是生效了，但设置的 Host 没有生效。是不是设置的 Host 被后面的 open 覆盖掉了，但是 open 又没提供 headers 设置参数。

[('User-Agent', 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/93.0.4577.63 Safari/537.36'), ('Host', 'qq.com')]
{
  "args": {}, 
  "data": "", 
  "files": {}, 
  "form": {
    "data": ""
  }, 
  "headers": {
    "Accept-Encoding": "identity", 
    "Content-Length": "4", 
    "Content-Type": "application/x-www-form-urlencoded", 
    "Host": "httpbin.org", 
    "User-Agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/93.0.4577.63 Safari/537.36", 
    "X-Amzn-Trace-Id": "Root=1-6146527f-471edcb1073f7ebe3e0672a3"
  }, 
  "json": null, 
  "origin": "123.203.104.151", 
  "url": "http://httpbin.org/post"
}