Minimal Python3 webserver (zero dependencies)

main.py

import http.server
import socketserver
from http import HTTPStatus
import os


class Handler(http.server.SimpleHTTPRequestHandler):
    def do_GET(self):
        self.send_response(HTTPStatus.OK)
        self.end_headers()
        self.wfile.write(b'Hello world')

port = os.environ.get("PORT") or "8080"

httpd = socketserver.TCPServer(('', int(port)), Handler)
print("Serving http://localhost:" + port)
httpd.serve_forever()