如何在tkinter python中强制选择单选按钮

import tkinter as tk

def on_radio_select():
    selected_value = radio_var.get()
    print("Selected:", selected_value)

root = tk.Tk()
root.title("选择单选按钮示例")

# 创建变量并设置初始值
radio_var = tk.StringVar()
radio_var.set("选项1")

# 创建单选按钮并分组
radio_btn1 = tk.Radiobutton(root, text="选项1", variable=radio_var, value="选项1")
radio_btn2 = tk.Radiobutton(root, text="选项2", variable=radio_var, value="选项2")
radio_btn3 = tk.Radiobutton(root, text="选项3", variable=radio_var, value="选项3")

# 绑定事件处理函数
radio_btn1.configure(command=on_radio_select)
radio_btn2.configure(command=on_radio_select)
radio_btn3.configure(command=on_radio_select)

# 布局单选按钮
radio_btn1.pack()
radio_btn2.pack()
radio_btn3.pack()

root.mainloop()