Add a scrollbar to tkinter - python 3

Question

I wish to add a scroll bar to the window that opens when i click on the retriever button - before anyone asks Yes this was once for a controlled assessment but now i am using the pre existing code to learn tkinter with

def retrieve():
    exist = os.path.isfile('messages.txt')
    if exist == True:

        w = Toplevel(master=gui)


        x = 1
        list = [i.strip().split() for i in open("messages.txt").readlines()]
        l = len(list)
        i = 0
        while i < l:
            x = str(x)
            Label(w, text = "input " + x).pack()
            Label(w, text = (list[i])).pack()
            i = i + 1
            Label(w, text ="offset " + x).pack()
            Label(w, text =(str(list[i]))).pack()
            i = i + 1
            Label(w, text ="output " + x).pack()
            Label(w, text =(list[i])).pack()
            i = i + 1
            Label(w, text =" ").pack()
            x = int(x)
            x = x + 1
    else:
        labelprint = "No Stored Messages"
        add = Label(gui, text = labelprint, width = 30)
        add.grid(row = 2, column =2)

gui = Tk()

gui.title("Encoder")

Button(gui, text="Retriever", command=retrieve).grid(row = 1, column = 0)

mainloop( )