MyButton1.grid(row=0, column=0)
MyButton2 = Button(master, text='BUTTON2', width=10, command=callback)
MyButton2.grid(row=1, column=0)
MyButton3 = Button(master, text='BUTTON3', width=10, command=callback)
MyButton3.grid(row=2, column=0)
Setting the position on a button in Python?