Python urllib Tunnel Proxy: Standard Library Four Scenarios

import urllib.request, os, ssl, time
 
host = os.getenv("PROXY_HOST", "t.16yun.cn")
port = os.getenv("PROXY_PORT", "31111")
user = os.getenv("PROXY_USERNAME", "user")
pwd = os.getenv("PROXY_PASSWORD", "password")
 
proxy_url = f"http://{user}:{pwd}@{host}:{port}"
ctx = ssl.create_default_context()
 
for i in range(1, 4):
    handler = urllib.request.ProxyHandler({"http": proxy_url, "https": proxy_url})
    https_handler = urllib.request.HTTPSHandler(context=ctx)
    opener = urllib.request.build_opener(handler, https_handler)
 
    req = urllib.request.Request("https://httpbin.org/ip",
        headers={"Connection": "close", "Proxy-Connection": "close"})
 
    with opener.open(req, timeout=15) as resp:
        print(f"Request {i}: {resp.read().decode()}")
    time.sleep(0.5)

handler = urllib.request.ProxyHandler({"http": proxy_url, "https": proxy_url})
opener = urllib.request.build_opener(handler, urllib.request.HTTPSHandler(context=ctx))
 
for i in range(1, 4):
    req = urllib.request.Request("https://httpbin.org/ip",
        headers={"Connection": "keep-alive", "Proxy-Connection": "keep-alive"})
    with opener.open(req, timeout=15) as resp:
        print(f"Request {i}: {resp.read().decode()}")
    time.sleep(0.2)

import http.client, base64, json
 
class TunnelHTTPSConnection(http.client.HTTPSConnection):
    def set_tunnel(self, host, port=None, headers=None):
        if headers is None:
            headers = {}
        headers["Proxy-Tunnel"] = os.getenv("PROXY_TUNNEL", "urllib-demo")
        super().set_tunnel(host, port, headers)
 
proxy_url = f"http://{user}:{pwd}@{host}:{port}"
conn = TunnelHTTPSConnection(host, int(port), context=ctx)
auth = base64.b64encode(f"{user}:{pwd}".encode()).decode()
conn.set_tunnel("httpbin.org", 443, headers={"Proxy-Authorization": f"Basic {auth}"})
conn.request("GET", "/ip")
resp = conn.getresponse()
print(resp.read().decode())