ghow to get avarauvle change from a radiobutton tkinter code example

Example: tkinter radio buttons

from Tkinter import *

master = Tk()

v = IntVar()

Radiobutton(master, text="One", variable=v, value=1).pack(anchor=W)
Radiobutton(master, text="Two", variable=v, value=2).pack(anchor=W)

mainloop()