How do I place a preset into the text box?

[Steve]

The following program compiles but does not quite do what I would like it to
do. Line 19 is the preset information but I do not seem to be able to get it
into the form by code.  My purpose is to let the user make changes without
having to re-enter the entire code.

Suggestions welcome.
Steve

#===========================================================
import tkinter as tk
from tkinter import ttk
import sys

window = tk.Tk()
window.title("Python Tkinter Text Box")
window.minsize(600,400)

def Submit():
    label.configure(text= 'The new code is: ' + NewCode.get())
    
def ClickExit():
    #This exit closes the program but the form remains and is still active.
    # I want only to close the form.
    print("Exiting")
    sys.exit()
    
OldCode = ("1234-abcd")

label = ttk.Label(window, text = "Enter the new code")
label.grid(column = 1, row = 1)

NewCode = tk.StringVar()
CodeEntered = ttk.Entry(window, width = 15, textvariable = NewCode)
CodeEntered.grid(column = 2, row = 3)

button = ttk.Button(window, text = "Submit", command = Submit)
button.grid(column= 2, row = 5)

button = ttk.Button(window, text = "Quit", command = ClickExit)
button.grid(column= 2, row = 7)

window.mainloop()

x = (NewCode.get())
print("The new code entered is: " + x)
      
#=================================================



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