次のページのサーバーサイドを PHP から、python に変えました。
jQuery を使ったログイン画面

login.html

<!DOCTYPE html>
<html lang="ja">
<head>
<meta http-equiv="Pragma" content="no-cache" />
<meta http-equiv="Cache-Control" content="no-cache" />
<meta http-equiv="CONTENT-TYPE" content="text/html; charset=utf-8" />
<script src="/js/jquery-3.4.0.min.js"></script>
<script src="login.js"></script>
<link href="login.css" rel="stylesheet">
<title>Login</title>
</head>
<body>
<div class="center">
<h2>ログイン画面</h2>
<table>
<tr><td>名前</td><td><input type="text" name ="userid" id ="userid"></td></tr>
<tr><td>パスワード&nbsp;</td><td><input type="text" name ="password" id="password"></td></tr>
</table>
<p />
<button id="submit">submit</button>
</div>
<p />
<div class="result"></div>
<p />
Jun/10/2017<p />
</body>
</html>

login.css

/* -------------------------------------------------------------------- */
/*
	login.css

					Jun/10/2017
*/
/* -------------------------------------------------------------------- */
.center
{
	width: 80%;
	margin: 0 auto;
}
/* -------------------------------------------------------------------- */

login.js

// ---------------------------------------------------------------
//	login.js
//
//						Jun/10/2017
// ---------------------------------------------------------------
jQuery(function()
{
	jQuery('#submit').on('click',function()
		{
		const url="login_check.py"

		const userid = jQuery('#userid').val()
		const password = jQuery('#password').val()
		const args = {"userid": userid,"password": password}

		jQuery.post (url,args,function (message)
			{
			var str_out = ""
			for (var it in message)
				{
				str_out += message[it] + "<br />"
				}
			jQuery('.result').html(str_out)
			console.log(data)
			})

	})
})

// ---------------------------------------------------------------

login_check.py

# ! /usr/bin/python3
# -*- coding: utf-8 -*-
#
#	login_check.py
#
#					Jun/10/2017
#
# --------------------------------------------------------------------
import	sys
import	cgi
import	json
# --------------------------------------------------------------------
def password_db_get_proc():
	password_db = {}
	password_db['scott'] = 'tiger'
	password_db['jack'] = 'jones'
	password_db['betty'] = 'smith'

	return	password_db
#
# --------------------------------------------------------------------
def hantei_proc(userid,password):
	password_db = password_db_get_proc()
	is_certificated = userid in password_db and password == password_db[userid]
	return	is_certificated
#
# --------------------------------------------------------------------
ff=cgi.FieldStorage()
#
userid = ff.getfirst("userid","")
password = ff.getfirst("password","")
#
message = []
hantei = hantei_proc(userid,password)
if hantei:
	message.append('OK')
else:
	message.append('NG')
#
message.append(userid)
message.append(password)
#
out_str = json.dumps(message)
print("Content-type: text/json\n\n")
print(out_str)
# --------------------------------------------------------------------