from tkinter import *

class Application(Frame):
    """ GUI application. """
    def __init__(self, master):
        """ Initialize the frame. """
        super(Application, self).__init__(master)
        self.grid()
        self.create_widgets()

        frame = Frame(master)
        frame.pack()

    def create_widgets(self):

        # create instruction label
        self.inst_lbl = Label(self, text = "Test")
        self.inst_lbl.grid(row = 1, column = 1, columnspan = 2, sticky = W)


        # create submit button
        self.submit_bttn = Button(self, text = "OK", command = ?????)
        self.submit_bttn.grid(row = 3, column = 2, sticky = W)

      # create submit button
        self.submit_bttn = Button(self, text = "Cancel", command = ????)
        self.submit_bttn.grid(row = 3, column = 4, sticky = W)


# main
root = Tk()
root.title("Test")
root.geometry("100x50")

app = Application(root)

root.mainloop()