Python乌龟wn.ontimer在if语句中

Question

I have Turtle commands in my code as you see below. I would like to put a timer on these commands inside an if statement. My current code just works like so:

'# WHEN USER PRESSES SPACE, LIGHT TURNS GREEN

'# WHEN LIGHT IS GREEN ARROW MOVES 50 PIXELS

        player1.pendown()
        player1.forward(50)
        player2.pendown()
        player2.forward(50)

The arrow really only moves once every time I press the space key. I would like to turn that into a timer so the arrow would move every 60 milliseconds until the user presses the space key again.

I tried using an wn.ontimer but I keep on messing up something. Below is how the code looks now:

def advance_state_machine():
    global state_num
    if state_num == 0:
        tess.forward(70)
        tess.fillcolor("red")
        state_num = 1
    else:
        tess.back(70)
        tess.fillcolor("green")
        state_num = 0
        player1.pendown()
        player1.forward(50)
        player2.pendown()
        player2.forward(50)


    wn.onkey(advance_state_machine, "space")

wn.listen()                   
wn.mainloop()

Answer 1

Your description of your problem is inconsistent and your code is out of sync with your description. Here's what I believe you stated you wanted your code to do:

The turtle moves forward 1 step every 60 milliseconds and alternates between red/forward and green/backward whenever the space bar is pressed.

I believe this code implements that, a key event is used to detect the space bar and a timer event is used to keep the turtle in motion:

from turtle import Turtle, Screen, mainloop

def advance_state_machine():
    global state_num

    wn.onkey(None, 'space')  # avoid overlapping events

    if state_num > 0:
        tess.fillcolor('green')
    else:
        tess.fillcolor('red')

    state_num = -state_num

    wn.onkey(advance_state_machine, 'space')

def advance_tess():
    tess.forward(state_num)
    wn.ontimer(advance_tess, 60)

wn = Screen()
tess = Turtle()
tess.fillcolor('red')

state_num = 1

wn.onkey(advance_state_machine, 'space')
wn.ontimer(advance_tess, 60)
wn.listen()

mainloop()

Make sure to click on the window to make it active before trying the space bar. Left unattended, the turtle will eventually go off screen.