Python Tkinter菜单系统。无法获取合计和显示的价格

import tkinter as tk

def on_menu_item_click():
    print("菜单项被点击")

root = tk.Tk()

menu_bar = tk.Menu(root)

file_menu = tk.Menu(menu_bar, tearoff=0)
file_menu.add_command(label="打开", command=on_menu_item_click)
file_menu.add_command(label="保存", command=on_menu_item_click)
menu_bar.add_cascade(label="文件", menu=file_menu)

edit_menu = tk.Menu(menu_bar, tearoff=0)
edit_menu.add_command(label="剪切", command=on_menu_item_click)
edit_menu.add_command(label="复制", command=on_menu_item_click)
menu_bar.add_cascade(label="编辑", menu=edit_menu)

root.config(menu=menu_bar)
root.mainloop()

def show_price():
    # 获取价格的逻辑
    price = get_price()
    print("价格：", price)

price_menu = tk.Menu(menu_bar, tearoff=0)
price_menu.add_command(label="显示价格", command=show_price)
menu_bar.add_cascade(label="价格", menu=price_menu)