Python tkinter Entry widget usage

I'm currently trying to use the entry widget in tkinter to get a number from the user, and then use that number to define a parameter of one of my other functions.

The code is very long, so I'll try summarize my thoughts after the block.

class NimGame():

    def __init__(self, numberOfBalls):
        self.numberOfBallsRemaining = numberOfBalls
        print("Nim game initialized with {} balls.".format(self.numberOfBallsRemaining))

    def remainingBalls(self):
        return self.numberOfBallsRemaining

    def take(self, numberOfBalls):
        if (numberOfBalls < 1) or (numberOfBalls > 3) or (numberOfBalls > self.numberOfBallsRemaining):
            print("You can't take that number of balls. Try again.")
            # ## Update Label in the GUI to tell user they can't take that many balls.
            # It might be better to "inactivate" the buttons that correspond to invalid number to take.
            statusLabel.configure(text="You can't take that number of balls. Try again.")
        else:
            self.numberOfBallsRemaining = self.numberOfBallsRemaining - numberOfBalls
            print("You took {} balls. {} remain.".format(numberOfBalls, self.numberOfBallsRemaining))
            if self.numberOfBallsRemaining == 0:
                print("Computer wins!")
            else:
                # ## After removing player-chosen balls, update graphics and then pause for 1.0 seconds
                # before removing computer-chosen balls.  This way the player can "see" the
                # intermediate status.  Perhaps think about a nicer way of showing this.
                updateGraphics()
                sleep(1.0)

                computerMaxBalls = min(3, self.numberOfBallsRemaining)
                compBallsTaken = random.randint(1,computerMaxBalls)
                self.numberOfBallsRemaining = self.numberOfBallsRemaining - compBallsTaken

                # ## After removing computer-chosen balls, update graphics again.
                updateGraphics()
                print("Computer took {} balls. {} remain.".format(compBallsTaken, self.numberOfBallsRemaining))
                if self.numberOfBallsRemaining == 0:
                    print("You win!")

def updateGraphics():
    canvas.delete('all')
    centerX = leftmostBallXPosition
    centerY = ballYPosition
    for i in range(nimGame.remainingBalls()):
        canvas.create_oval(centerX - halfBallSize,
                           centerY - halfBallSize,
                           centerX + halfBallSize,
                           centerY + halfBallSize,
                           fill="#9999ff")
        centerX = centerX + spaceBetweenBalls + ballSize
        canvas.update_idletasks()

def initializeNewGame():
    numberOfBalls = e1.get()
    initializeNimAndGUI(numberOfBalls)

def initializeNimAndGUI(numberOfBalls):
    global nimGame
    global ballSize, halfBallSize, spaceBetweenBalls, leftmostBallXPosition, ballYPosition

    nimGame = NimGame(numberOfBalls)

    canvas.delete('all') 
    ballSize = min(maxBallSize, int(((canvasWidth-canvasBorderBuffer)//numberOfBalls)/1.2))
    halfBallSize = ballSize // 2
    spaceBetweenBalls = int(0.2 * ballSize)
    leftmostBallXPosition = (canvasBorderBuffer//2) + (spaceBetweenBalls//2) + halfBallSize
    ballYPosition = canvasHeight // 2
    updateGraphics()

 def createGUI():
    global rootWindow
    global canvas
    global statusLabel
    global textEntry
    global e1

    rootWindow = Tk()
    canvasAndButtons = Frame(rootWindow)
    canvas = Canvas(canvasAndButtons, height=canvasHeight, width=canvasWidth, relief=SUNKEN, borderwidth=2)
    canvas.pack(side=LEFT)

    buttonframe = Frame(canvasAndButtons)
    e1 = Entry(buttonframe)
    e1.pack()
    button1 = Button(buttonframe, text='Take 1', command=lambda:takeBalls(1))
    button2 = Button(buttonframe, text='Take 2', command=lambda:takeBalls(2))
    button3 = Button(buttonframe, text='Take 3', command=lambda:takeBalls(3))
    button4 = Button(buttonframe, text='New Game', command=initializeNewGame)
    button1.pack()
    button2.pack()
    button3.pack()
    button4.pack()
    buttonframe.pack(side=RIGHT)
    canvasAndButtons.pack()
    statusLabel = Label(rootWindow, text="Play Nim")
    statusLabel.pack()

def runNim(numberOfBalls):
    createGUI()
    initializeNimAndGUI(numberOfBalls)   
    rootWindow.mainloop()

So to me it seems that the program is having issues updating the graphics when I do a second game. What should happen is that, for example, i call runNim(20) and play a game with 20 balls. After the game, I need to be able to enter a number in the entry widget, click new game, and have that be the new numberOfBalls. When I do that, I get the init message back stating "Nim game initialized with 10 balls." But the GUI doesnt change, no balls appear in the GUI, and if I try to take anything it gives traceback and errors.