# Tk_spectrum_cycle.py

# Tk_spectrum_cycle.py

from Tkinter import *

root = Tk()
root.title("Spectrum Cycle")
root.geometry("120x120")
wi = 120
he = 120

r = 0
g = 0
b = 255

w = Canvas(root, width=wi, height=he, bg="grey")
w.pack()

def update():
    pass

def color(r,g,b):
    c = '#%02x%02x%02x' %(r,g,b)
    try:
        w.create_rectangle(0,0,wi,he,fill=c)
        root.update()
    except: pass

def run():
    global r,g,b

    # blue to violet
    for r in range(0, 255, 4):
        color(r,g,b)

    # violet to red
    for b in range(255, 0, -4):
        color(r,g,b)

    # red to yellow
    for g in range(0, 255, 4):
        color(r,g,b)

    # yellow to green
    for r in range(255, 0, -4):
        color(r,g,b)

    # green to teal
    for b in range(0, 255, 4):
        color(r,g,b)

    # teal to blue
    for g in range(255, 0, -4):
        color(r,g,b)

    root.after(1, run)

run()
root.mainloop()