Getting value of radiobutton trouble

[VK]

Hi!
What I'm missing in following code? Cannot get the values of 
radiobuttons. Starting only one class (GetVariant), it works. When I put 
two classes together, it doesn't.
Regards, VK

from Tkinter import *
class GetVariant:
     def __init__(self):
         self.root = Tk()
         self.mainframe = Frame(self.root,bg="yellow")
         self.mainframe.pack(fill=BOTH,expand=1)

         self.firstframe = Frame(self.mainframe,bg="red")
         self.firstframe.pack(side=BOTTOM,expand=1)

         global v
         v = StringVar()
         self.radiobutton = Radiobutton(self.firstframe,text= "Variant 
1", variable=v, value="Variant 1")
         self.radiobutton.pack(side=TOP,anchor=W)
         self.radiobutton.select()
         self.radiobutton = Radiobutton(self.firstframe,text= "Variant 
2", variable=v, value="Variant 2")
         self.radiobutton.pack(side=TOP,anchor=W)
         self.radiobutton = Radiobutton(self.firstframe,text= "Variant 
3", variable=v, value="Variant 3")
         self.radiobutton.pack(side=TOP,anchor=W)



         self.secondframe = Frame(self.mainframe,bg="blue")
         self.secondframe.pack()
         self.var = Button(self.secondframe,text="What 
Variant",command=self.call)
         self.var.pack(expand=1,side=BOTTOM)



     def call(self):
         self.variant = v.get()
         print 'Input => "%s"' % self.variant

class OneButton:
         def __init__(self):
             self.root = Tk()
             Button(self.root,text="click me",command=self.getvar).pack()
         def getvar(self):
             a=GetVariant()

d = OneButton()
d.root.mainloop()