Newbie alert

[Valone, Toren W.]

Ok, new to Python and Tkinter.. Following along examples in book, got to
dialog windows example coded this

# dialog1.py

from Tkinter import *

class Mydialog:

  def _int_(self,parent):

        top = self.top = Toplevel(parent)

        Label(top, text="Value").pack()

        self.e = Entry(top)
        self.e.pack(padx=5)

        b = Button(top,text="OK", command=self.ok)
                   
        b.pack(pady=5)

  def ok(self):

        print "value is", self.e.get()
        self.top.destroy()

root = Tk()
Button(root, text="Hello!").pack()
root.update()

d = MyDialog(root)

root.wait_window(d.top)               

When I run it IDLE 

gives me this

Traceback (most recent call last):
  File "C:/Python24/dialog1.py", line 29, in -toplevel-
    d = MyDialog(root)
NameError: name 'MyDialog' is not defined

I have a feeling this is something very simple, but I cannot figure it out.
Help!