在tkinter中绘图时程序不会结束

import tkinter as tk

def draw_circle():
    canvas.create_oval(50, 50, 150, 150, fill='red')

def close_window():
    root.destroy()

root = tk.Tk()
canvas = tk.Canvas(root, width=200, height=200)
canvas.pack()

draw_button = tk.Button(root, text='Draw Circle', command=draw_circle)
draw_button.pack()

close_button = tk.Button(root, text='Close', command=close_window)
close_button.pack()

root.mainloop()