Canvas - Drawing Ovals

The first code is a simple example:

import Tkinter
root    =  Tkinter.Tk()
ch, cw  =  200, 200
c1 = Tkinter.Canvas(root, height = ch, width = cw, bg = "black")
c1.create_oval(30, 30, 175, 175, outline = "yellow", width = 2)