Beginner - GUI toggle button

Can i ask for a little help please? I've created a GUI with a toggle button which toggles the LED ON, LED OFF.

What i would like to do now is add some code to change the text of the button as it toggles between the two states.

I've looked up some examples but I can't quite see how, or where, to add the code to make the button text toggle as well.

Thanks for any help.

My code....

# Idle 07_02_LED ON using GUI
from time import sleep

from Tkinter import *

class App:

    def __init__(self, master): 
        frame = Frame(master)
        frame.pack()
        Label(frame, text='Turn LED ON').grid(row=0, column=0)

        Label(frame, text='Turn LED OFF').grid(row=1, column=0)

        button = Button(frame, text='LED 0 ON', command=self.convert0)
        button.grid(row=2, columnspan=2)


    def convert0(self, tog=[0]):

        tog[0] = not tog[0]
        if tog[0]:
        print('LED 0 OFF')

        else:
        print('LED 0 ON')

root = Tk()

root.wm_title('LED on & off program')

app = App(root)

root.mainloop()