To still answer your question. Above code does not create an object of the given class. You can consider class as a template as to what your object will look like. Using this class you can create an object in some other function (where you wish to use it) . And the function where you create the object will then invoke display() method on that object.
root = tkinter.Tk()
buttons=[i for i in range(10)]
#If specific button is pressed, output "YES"
for num in buttons: