[Tutor] why do I not get a Window Title with the following?

[Girish Gajwani]

Please check the following code:

#######################
#! /usr/bin/env  python 

import string
from Tkinter import *

root = Tk()
root.title="girish"
root.mainloop()
#######################

All I am trying  is to change the window title to something
else("girish", here)
I have seen some other code do something like this and work.
However, I could not get this even in this small piece of
code. Obviously I must be doing something silly :-). But i
could not find out what was the silly thing I was doing.

Please help

TIA
Girish
PS: I am trying to learn Tkinter