无法选中tkinter框架中的多个Checkbuttons

import tkinter as tk

def show_selected():
    selected = [var.get() for var in vars]  # 获取每个Checkbutton的状态
    print(selected)  # 打印选中的状态

root = tk.Tk()

vars = []
checkbuttons = []

# 创建多个Checkbuttons并绑定到IntVar()变量
for i in range(3):
    var = tk.IntVar()
    vars.append(var)
    checkbutton = tk.Checkbutton(root, text=f"Option {i+1}", variable=var)
    checkbutton.pack()
    checkbuttons.append(checkbutton)

# 创建一个按钮，点击时显示选中的状态
button = tk.Button(root, text="Show Selected", command=show_selected)
button.pack()

root.mainloop()