Python - example [FB:learnpython.org]

while True:

    usr_command = input("Type 'play' to start, type 'stop' to quit: ")
    usr_command = usr_command.strip().lower() # remove some spaces and convert to lower

    if usr_command == "stop":
        break    # leave `while` loop
    if usr_command != "play":
        continue # return to the beginning of `while` loop and ask again

    print("now we can play")