tk.radiobutton的值冲突

Question

在ShowChoice中打印的

tk.Radiobutton值（v.get（））是正确的，但是当我尝试在函数外部评估ShowChoice时，该值保持在初始值。我在使用'return'吗 错误地？

import Tkinter as tk
root = tk.Tk()
v = tk.IntVar()
v.set(0)  # initializing the choice, i.e. python
def ShowChoice():  
    x = v.get()    # these values are correct
    print  x
    return x
radio1 = tk.Radiobutton(root, text='python', padx = 20,variable=v, command=ShowChoice, value=0)  
radio1.pack(anchor=tk.W)               
radio2 = tk.Radiobutton(root, text='java', padx = 20, variable=v,command=ShowChoice, value=1)
radio2.pack(anchor=tk.W)              
q = ShowChoice()   # this does not show the    
print q            # the value for the last
root.mainloop()    # button pushed