python 简单的小菜单

import tkinter as tk
from tkinter import ttk
from tkinter import scrolledtext
from tkinter import Menu
def _quit():
    win.quit()
    win.destroy()
    exit() 
win = tk.Tk()
win.title("菜单练习")
book = Menu(win)
win.config(menu = book)
file_menu = Menu(book,tearoff = 0)
file_menu.add_command(label = "New")
file_menu.add_separator()
file_menu.add_command(label = "Exit",command = _quit)
book.add_cascade(label = "File",menu = file_menu)
win.mainloop()