while True:
    if something is pressed:
        print("STOP")
        break
    do_something()

while True:
    i = input() or None if program wait > 3 seconds. # > = more than
    if != None:
        print("STOP")
        break
    do_something()

while True:
    try:
        do_something()
    except KeyboardInterrupt:
        pass