Traffic Light GUI

#Imports the required libraries
from time import sleep
from tkinter import *

#This procedure manages which light order is currently being displayed
def loop_lights():
    red=["red","white","white"]
    red_yellow=["red","yellow","white"]
    yellow=["white","yellow","white"]
    green=["white","white","green"]
    off=["white","white","white"]

    arrangement_order=[red,red_yellow,yellow,green,off]

    current_light_order = 0
    while True:

        if current_light_order > 4:
            current_light_order = 0

        else:
            draw_lights(arrangement_order[current_light_order])
            current_light_order += 1
            sleep(2)

#This procedure actually draws the lights when asked to by the previous procedure
def draw_lights(light_order):
    canvas.delete("all")
    canvas.create_oval(5,5,145,145,fill=light_order[0])
    canvas.create_oval(5,150,145,295,fill=light_order[1])
    canvas.create_oval(5,300,145,445,fill=light_order[2])
    canvas.update()


#This code manages the creation of the GUI
main_window = Tk()

button_start = Button(main_window, text="Start!", command=loop_lights)
canvas = Canvas(main_window, width=150, height=450)

button_start.pack()
canvas.pack()

main_window.mainloop()