import socket
from time import sleep

sock = socket.socket()
sock.bind(('', 9090))
sock.listen(1)
conn, addr = sock.accept()

def give_me_a_world():
    sleep(1)
    return b'world'

while True:
    data = conn.recv(1024)
    response = b'HTTP/1.1 200 OK\r\n'\
               b'Content-Length: 12\r\n'\
               b'Connection: keep-alive\r\n'\
               b'\r\n'\
               b'hello, '

    conn.send(response) # send first part
    conn.send(give_me_a_world()) # make a delay and send other part

conn.close()