reddit.py

import tkinter as tk

root = tk.Tk()
root.wm_title('Radio Buttons')

label1 = tk.Label(root)
label1.config(text='Please select an option below.')
label1.pack()


def update_label2(option, value):
    selection = "current selection is: \n\n" + str(option) + ": " + str(value)
    label2.config(text=selection)

var = tk.IntVar()
var.set(100)

R1 = tk.Radiobutton(root, text='A', value=100, variable=var,
                    command=lambda: update_label2('A', 100))
R1.pack(anchor='center')
R2 = tk.Radiobutton(root, text='B', value=80, variable=var,
                    command=lambda: update_label2('B', 80))
R2.pack(anchor='center')
R3 = tk.Radiobutton(root, text='C', value=60, variable=var,
                    command=lambda: update_label2('C', 60))
R3.pack(anchor='center')


label2 = tk.Label(root)
label2.config(text='Current selection is: \n \nA: 100')
label2.pack()

root.mainloop()

Edited to utilize lambda for the callbacks from the radio buttons to the function that sets the label text.