A simple example of selector usage in Python

selector_demo.py

import socket
import selectors

sel = selectors.DefaultSelector()

def accept_connection(server_sock):
    conn, addr = server_sock.accept()
    print(f"Accepted connection from {conn} | {addr}");
    conn.setblocking(False);
    sel.register(conn, selectors.EVENT_READ, read_data)

def read_data(conn):
    data = conn.recv(1024)
    if data:
        print(f"Recieved: {data.decode().strip()}")
        conn.sendall(b"pam pam")
    else:
        print("Closing connection")
        sel.unregister(conn)
        conn.close()

server_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_sock.bind(("localhost", 7777))
server_sock.listen()
server_sock.setblocking(False)
sel.register(server_sock, selectors.EVENT_READ, accept_connection)

print("Server running on localhost:7777")

while True:
    events = sel.select(timeout=None)
    for key, mask in events:
        callback = key.data
        callback(key.fileobj)