在tkinter python中为单选按钮指定默认值

import tkinter as tk

root = tk.Tk()

# 创建一个IntVar变量，并设置初始值为1
selected_value = tk.IntVar(value=1)

# 创建单选按钮，并将variable参数设置为selected_value
radio_button1 = tk.Radiobutton(root, text="选项1", variable=selected_value, value=1)
radio_button2 = tk.Radiobutton(root, text="选项2", variable=selected_value, value=2)
radio_button3 = tk.Radiobutton(root, text="选项3", variable=selected_value, value=3)

radio_button1.pack()
radio_button2.pack()
radio_button3.pack()

root.mainloop()