import Tkinter as tk

root = tk.Tk()
canvas = tk.Canvas(root, width=128, height=256, highlightthickness=0)
canvas.pack()

for y in range(0, 256):
    color = "#%02X%02X%02X" % (y, y, y)
    canvas.create_rectangle(0, y, 128, y + 1, fill=color, width=0)

root.mainloop()
