Python/Tkinter: why does the .get method of IntVar shows same value when clicking different radiobuttons?

Brief overview of the programme:

1. When launching script, the dialog window is appearing and asking you to select directory path (class MyApp)
2. When selected - one need to push "Start Monitoring" button. This action withdraw main window (root) and initialize container (class FrameContainer) consisting of two frames, namely 'PageOne' and 'PageTwo' (see corresponding classes).
3. Button "Back Home" on "Page One" should destroy the instance of class FrameContainer and show again the dialog window - this action is realized using methods .update() and .deiconify().
4. Selection of any of the radiobuttons on "Page One" should change the value of variable "rb_indx" - it is realized using .get() method of IntVar.

Problems:

• Radiobuttons are initialized in wrong way. The var.set(1) - should highlight the 'var1' button, however in my case are highlighted 'var2' and 'var3'.
• The .get() method of IntVar does not update the value of the variable 'rb_indx' when selecting radiobutton. // print rb_indx always give 1
• When closing 'PageOne' window by the [x] (in coer of the screen), the dialog window is not appearing, however is expected...

I will strongly appreciate any ideas or clues regarding abovementioned problems. Thanks!

The code:

# -*- coding: utf-8 -*-

try:
    # Python2
    import Tkinter as Tk
    from Tkinter import IntVar
    from tkFileDialog import askdirectory

except ImportError:
    # Python3
    import tkinter as Tk
    from tkinter import IntVar
    from tkinter.filedialog import askdirectory

LARGE_FONT=("Verdana", 12)

########################################################################

class FrameContainer(Tk.Tk):

    def __init__(self, parent):

        self.original_frame = parent   

        Tk.Tk.__init__ (self)
        container = Tk.Frame(self)

        container.pack(side="top", fill="both", expand = True)
        container.grid_rowconfigure(0, weight=1)
        container.grid_columnconfigure(0, weight =1)

        self.frames = {}

        for F in (PageOne, PageTwo): 

            frame = F(container, self)
            self.frames[F] = frame
            frame.grid(row=0, column=0, sticky="nsew")

        self.show_frame(PageOne)

    def show_frame (self, cont):

        frame=self.frames[cont]
        frame.tkraise()

    def onClose(self):

        self.destroy()
        self.original_frame.show()  

class PageOne(Tk.Frame):

    def __init__(self, parent, controller):

        Tk.Frame.__init__(self, parent)

        label = Tk.Label(self, text="Page One", font=LARGE_FONT)
        label.pack(pady=10, padx=10)

        button1=Tk.Button(self, text="Back to Home", command=lambda: controller.onClose())
        button1.pack()

        button2=Tk.Button(self, text="Page Two", command=lambda: controller.show_frame(PageTwo))
        button2.pack()

        def get_button_indx(): 

            global rb_indx
            rb_indx=var.get()
            print rb_indx

        var.set(1)

        names_tuple = ('var1', 'var2', 'var3')

        for col_numb in range (1,len(names_tuple)+1):
            radio = Tk.Radiobutton(self, text=names_tuple[col_numb-1], variable=var, value=col_numb, command=get_button_indx)
            radio.pack()

class PageTwo(Tk.Frame):

    def __init__(self, parent, controller):

        Tk.Frame.__init__(self, parent)

        label = Tk.Label(self, text="Page Two", font=LARGE_FONT)
        label.pack(pady=10, padx=10)

        button1=Tk.Button(self, text="Back to Home", command=lambda: controller.onClose())
        button1.pack()

        button2=Tk.Button(self, text="Page One", command=lambda: controller.show_frame(PageOne))
        button2.pack()

class MyApp(object):

    def __init__(self, parent):

        self.root = parent
        self.root.title("Start page")
        self.frame = Tk.Frame(parent)
        self.frame.pack()

        def choosedir():   

            global path_usr_var 
            path_usr_var = askdirectory()
            print path_usr_var

        button1 = Tk.Button(self.frame, text="Select Directory", command=choosedir)
        button1.pack(pady=10, padx=10)

        button2 = Tk.Button(self.frame, text="Start Monitoring", command=self.openFrame)
        button2.pack(pady=10, padx=10)

    def hide(self):
        self.root.withdraw()

    def openFrame(self):
        self.hide()
        firstFrame = FrameContainer(self)

    def show(self):
        self.root.update()
        self.root.deiconify()

########################################################################

if __name__ == "__main__":

    root = Tk.Tk()
    root.geometry("800x600")
    var = IntVar()
    app = MyApp(root)
    root.mainloop()