import turtle           # Tess becomes a traffic light.

wn = turtle.Screen()

wn.bgcolor("lightgreen")
tess = turtle.Turtle()
alex=turtle.Turtle()
sak=turtle.Turtle()
alex.penup()
sak.penup()
sak.speed(0)
alex.speed(0)
alex.hideturtle()

sak.hideturtle()
def draw_housing(tessa):
    """ Draw a nice housing to hold the traffic lights """
    tessa.pensize(3)
    tessa.color("black", "grey")
    tessa.begin_fill()
    tessa.forward(60)
    tessa.left(90)
    tessa.forward(100)
    tessa.circle(30, 180)
    tessa.forward(100)
    tessa.left(90)
    tessa.end_fill()

draw_housing(tess)

tess.penup()

# Position tess onto the place where the green light should be

tess.forward(30)
tess.left(90)
tess.forward(20)
# Turn tess into a big green circle
tess.shape("circle")
tess.pensize(3)
tess.fillcolor("green")
sak.shape("circle")

sak.fillcolor("dark orange")
sak.forward(30)
sak.left(90)
sak.showturtle()

sak.forward(60)
alex.shape("circle")

alex.fillcolor("dark red")
alex.forward(30)
alex.left(90)
alex.forward(100)
alex.showturtle()

# A traffic light is a kind of state machine with three states,
# Green, Orange, Red.  We number these states  0, 1, 2
# When the machine changes state, we change tess' position and
# her fillcolor.

# This variable holds the current state of the machine
state_num = 0
time=3000

def advance_state_machine():
    global state_num
    global time
    if state_num == 0:       # Transition from state 0 to state 1
        tess.fillcolor('green')
        alex.fillcolor('dark red')
        sak.fillcolor('dark orange')
        state_num = 1
        time=3000
        
    elif state_num == 1:     # Transition from state 1 to state 2
        sak.fillcolor('orange')
        tess.fillcolor('green')
        alex.fillcolor('dark red')
        time=1000
        state_num = 2
    elif state_num == 2:     # Transition from state 2 to state 3
        sak.fillcolor('orange')
        tess.fillcolor('dark green')
        alex.fillcolor('dark red')
        state_num = 3
        time=1000
    
    else:                    # Transition from state 2 to state 0
        sak.fillcolor('dark orange')
        tess.fillcolor('dark green')
        alex.fillcolor('red')
        state_num = 0
        time=2000
    
    wn.ontimer(advance_state_machine,time)
# Bind the event handler to the space key.
advance_state_machine()

wn.mainloop()

Traf

fic

light

traffic light .py (turtles)