'''
题目：画椭圆ellipse　　　
1.程序分析：
2.程序源代码：
'''
if __name__ == '__main__':
    from Tkinter import *
    x = 360
    y = 160
    top = y - 30
    bottom = y - 30
    
    canvas = Canvas(width = 400,height = 600,bg = 'white')
    for i in range(20):
        canvas.create_oval(250 - top,250 - bottom,250 + top,250 + bottom)
        top -= 5
        bottom += 5
    canvas.pack()
    mainloop()