from tkinter import *

class Window(Frame):
    def __init__(self, master=None):
        Frame.__init__(self, master)   
        self.master = master
        self.init_window()

    def init_window(self):
        self.master.geometry("400x300")
        self.master.title("GUI")
        self.pack(fill=BOTH, expand=1)
        menu = Menu(self.master)
        self.master.config(menu=menu)
        file = Menu(menu)
        file.add_command(label="Exit", underline=1, accelerator='Ctrl+w', command=self.client_exit)
        self.bind_all("<Control-w>", self.client_exit)
        menu.add_cascade(label="File", underline=0, menu=file)
        edit = Menu(menu)
        edit.add_command(label="Undo", underline=0)
        menu.add_cascade(label="Edit", underline=0, menu=edit)
    
    def client_exit(self, event=None):
        exit()
        
root = Tk()
app  = Window(root)
root.mainloop()