if user clicked the button computer will automaticly shutdown.

from tkinter import *
from tkinter import ttk
from tkinter import messagebox
import os

root = Tk()
root.title("Shutdown App")
root.geometry("250x100")

def shutdown():
  os.system("shutdown /s /t 1")

def cancel():
  os.system("shutdown /a")
  messagebox.showinfo("Shutdown Canceled", "Shutdown was canceled by the user")

button = ttk.Button(root, text="Shutdown", command=shutdown)
button.pack()

button2 = ttk.Button(root, text="Cancel", command=cancel)
button2.pack()

root.mainloop()