tk_oop.py

import Tkinter as tk

class NameOfYourApp(tk.Tk):
    def __init__(self, *args, **kwargs):
        tk.Tk.__init__(self, *args, **kwargs)
        # sets it to full screen (but windowed) on OS X
        self.geometry("{0}x{1}+0+0".format(self.winfo_screenwidth(), self.winfo_screenheight()))

        self.menubar = tk.Menu(self)
    
        self.filemenu = tk.Menu(self.menubar, tearoff=0)
        self.editmenu = tk.Menu(self.menubar, tearoff=0)
        self.helpmenu = tk.Menu(self.menubar, tearoff=0)

        self._initUI()

    def _initUI(self):
        self.filemenu.add_command(label="New", command=self.say_hi)
        self.filemenu.add_command(label="Open", command=self.say_hi)
        self.filemenu.add_command(label="Save", command=self.say_hi)
        self.filemenu.add_command(label="Save as...", command=self.say_hi)
        self.filemenu.add_separator()
        self.filemenu.add_command(label="Exit", command=self.quit)

        self.editmenu.add_command(label="Undo", command=self.say_hi)
        self.editmenu.add_separator()
        self.editmenu.add_command(label="Cut", command=self.say_hi)
        self.editmenu.add_command(label="Copy", command=self.say_hi)
        self.editmenu.add_command(label="Paste", command=self.say_hi)
        self.editmenu.add_command(label="Delete", command=self.say_hi)
        self.editmenu.add_command(label="Select All", command=self.say_hi)

        self.helpmenu.add_command(label="Help Index", command=self.say_hi)
        self.helpmenu.add_command(label="About...", command=self.say_hi)

        self.menubar.add_cascade(label="File", menu=self.filemenu)
        self.menubar.add_cascade(label="Edit", menu=self.editmenu) 
        self.menubar.add_cascade(label="Help", menu=self.helpmenu)

        self.config(menu=self.menubar)

    def say_hi(self):
        pass

def main():
    app = NameOfYourApp()
    app.mainloop()

if __name__ == '__main__':
    main()