Programa de paint.

from Tkinter import *

canvas_width = 500
canvas_height = 150




def paint(event):
    x1,y1 = (event.x - 1),(event.y - 1)
    x2,y2 = (event.x + 1),(event.y + 1)
    panel.create_oval(x1,y1,x2,y2, fill = "red")

def borrartodo():
    panel.delete("all")

master = Tk()
master.title("Pinta con el mouse")
panel = Canvas(master, width = canvas_width, height = canvas_height)
panel.pack(expand = YES, fill = BOTH )
panel.bind("", paint)

mensaje = Label(master, text = "Presione o arrastre con el mouse")
mensaje.pack(side = BOTTOM)

boton = Button(master, text = "Borrar", command = borrartodo)
boton.pack(side = BOTTOM)

master.mainloop()