Выводит ошибку AttributeError

from tkinter import *
def test1_comm():
    global price_br
    if br.get() == 1:
        price_br = 5000
    elif br.get() == 2:
        price_br = 9000
def test2_comm():
    global price_comm
    if comm.get() == 1:
        price_comm = 6000
    elif comm.get() == 2:
        price_comm = 10000
def calc():
    global price_br, price_comm, price
    price = price_br + price_comm
    label.config(text=str(price))
root = Tk()
price_br = 0
price_comm = 0
price = price_br + price_comm
label = Label(text='{} рублей'.format(price)).pack()
br = StringVar()
br.set('1')
frame1 = Frame(root, height=30)
frame1.pack(fill=X, pady=5)
label1 = Label(frame1, text='Строка1:').pack(side=LEFT)
frame2 = Frame(root, height=30)
frame2.pack(fill=X, pady=5)
var = IntVar()
br1 = Radiobutton(frame2, text='1', value=1, variable=var, command=test1_comm).pack(side=LEFT)
frame3 = Frame(root, height=30)
frame3.pack(fill=X, pady=5)
br2 = Radiobutton(frame3, text='2', value=2, variable=var, command=test1_comm).pack(side=LEFT)
frame10 = Frame(root, height=30)
frame10.pack(fill=X, pady=5)
label2 = Label(frame10, text='Строка2:').pack(side=LEFT)
comm = StringVar()
comm.set('1')
var2 = IntVar()
frame11 = Frame(root, height=30)
frame11.pack(fill=X, pady=5)
comm1 = Radiobutton(frame11, text='1', value=1, variable=var2, command=test2_comm).pack(side=LEFT)
frame12 = Frame(root, height=30)
frame12.pack(fill=X, pady=5)
comme2 = Radiobutton(frame12, text='2', value=2, variable=var2, command=test2_comm).pack(side=LEFT)
btn = Button(root, text='Рассчитать', command=calc).pack()
root.mainloop()