Difference between tkinter and Tkinter

It's simple.

For python2 it is:

from Tkinter import *

For python3 it is:

from tkinter import *

Here's the way how can you forget about this confusion once and for all:

try:
    from Tkinter import *
except ImportError:
    from tkinter import *

Tkinter is Python 2.x's name for the Tkinter library. In Python 3.x however, the name was changed to tkinter. To avoid running into this problem, I usually do this:

from sys import version_info
if version_info.major == 2:
    # We are using Python 2.x
    import Tkinter as tk
elif version_info.major == 3:
    # We are using Python 3.x
    import tkinter as tk