Live-Updating Graph

Question

So I have the following code:

class GooglePage(tk.Frame): 
    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        label = tk.Label(self, text="Google (GOOG)", font=LARGEFONT)
        label.pack(pady=10,padx=10)
        button1 = ttk.Button(self, text="Back to Home",
                            command=lambda: controller.show_frame(StartPage))
        button1.pack()
        f = Figure(figsize=(5,5), dpi=100)
        a = f.add_subplot(111)
        a.plot(x, y)
        canvas = FigureCanvasTkAgg(f, self)
        canvas.draw()
        canvas.get_tk_widget().pack(side=tk.BOTTOM, fill=tk.BOTH, expand=True)
        toolbar = NavigationToolbar2Tk(canvas, self)
        toolbar.update()
        canvas._tkcanvas.pack(side=tk.TOP, fill=tk.BOTH, expand=True)

So later on in the script, I define x and y to be lists that get 1 more element per second. However, a does not update. I need to know how to get a to update with x and y.

The first thing I tried was to use a while True loop inside the init function. It didn't run anything after the class declaration of GooglePage, including more class declarations and important stuff. I also tried to update a outside the class declaration, when I updated the lists. However, a, GooglePage.a , and GooglePage.__init__.a all throw errors.