#!/usr/bin/env python3
# -*- coding: utf-8 -*-
import os
import sys
from tkinter import *

class Dialog(Toplevel):
    '''Dialog class'''
    def __init__(self, parent, title=None):
        Toplevel.__init__(self, parent)
        self.geometry('+{0:d}+{1:d}'.format(parent.winfo_rootx()+20,
                                            parent.winfo_rooty()+20))
        self.resizable(0, 0)
        self.transient(parent)

        if title:
            self.title(title)
        self.parent = parent
        self.buttonbox()
        body = Frame(self)
        body.grid(column=0, row=0, padx=5, pady=5)

        self.initial_focus = self.body(body)
        if not self.initial_focus:
            self.initial_focus = self
        self.initial_focus.focus_set()
        self.protocol('WM_DELETE_WINDOW', self.cancel)

        self.grab_set()
        self.wait_window(self)

    def body(self, master):
        pass

    def button box(self):
        box = Frame(self)
        self.button1 = b1 = Button(box, text='OK', width=10,command=self.ok, default=ACTIVE)
        self.button2 = b2 = Button(box, text='Cancel', width=10, command=self.cancel)
        b1.pack(side=LEFT, padx=5, pady=5)
        b2.pack(side=LEFT, padx=5, pady=5)
        box.grid(column=0, row=1)

    def ok(self, event=None):
        if not self.validate():
            self.initial_focus.focus_set()
            return
        self.withdraw()
        self.update_idletasks()
        self.apply()
        self.cancel()

    def cancel(self, event=None):
        self.parent.focus_set()
        self.destroy()

    def validate(self):
        return True

    def apply(self):
        pass

class Application(Frame):
    def __init__(self, master):
        Frame.__init__(self, master)
        self.pack(expand=True, fill='both')
        Button(self, text='Open', command=self.open_dialog).pack()
        Button(self, text='Quit', command=master.destroy).pack()
        self.createMenu(master)

    def createMenu(self, master):
        menubar = Menu(master)
        master.config(menu=menubar)
        file_menu = Menu(menubar, tearoff=False)
        menubar.add_cascade(label='File', menu=file_menu)
        file_menu.add_command(label='Open', under=0, command=self.open_dialog)

    def open_dialog(self):
        class My_Dialog(Dialog):
            def body(self, master):
                Label(master, text='Label').grid(column=0, row=0)
                self.e = Entry(master, width=20)
                self.e.grid(column=1, row=0)
                return self.e

        d = My_Dialog(self.master)

root = Tk()
app = Application(master=root)
app.mainloop()