python_gui_example.py

#!/usr/bin/env python      1
import Tkinter as tk       2

class Application(tk.Frame):              3
    def __init__(self, master=None):
        tk.Frame.__init__(self, master)   4
        self.grid()                       5
        self.createWidgets()

    def createWidgets(self):
        self.quitButton = tk.Button(self, text='Quit',
            command=self.quit)            6
        self.quitButton.grid()            7

app = Application()                       8
app.master.title('Sample application')    9
app.mainloop()                            10

You may have to specificate your version of python, in fact, Tkinter is specifical to Python 2.6 and less.
But to pyhton3 the library's name is tkinter, (and not Tkinter).
So, it's better to use the last version of python, that is to say python3.