#---------------------------------------------------------------------
# Esempio conferma chiusura finestra
#---------------------------------------------------------------------

try:
    import Tkinter as tk                        # Py2
    import tkMessageBox as messagebox
except ImportError:
    import tkinter as tk                        # Py3
    import tkinter.messagebox as messagebox

#---------------------------------------------------------------------

class Applicazione:

    def __init__ (self):
        self.form1 = tk.Tk()
        self.form1.protocol("WM_DELETE_WINDOW", self.domanda)

    def domanda(self):
        if messagebox.askyesno("", "Chiudere veramente?"):
            self.form1.destroy()

    def start(self):
        self.form1.mainloop()

#---------------------------------------------------------------------

Applicazione().start()