[Tutor] Tkinter: Can's figure out how to put a frame in a second window

[Chris Roy-Smith]

Hi.

running Linux, with python3.6

I am trying to learn how to put a frame on a second window. I get no 
errors showing in the terminal, and I get no traceback.

What is happening is that the contents of the frame appear in the master 
window. I was expecting them to show in the second window. Also I 
expected the frame to be sunken, but there is no obvious signs of the 
frame, not even a colored background.

What am I doing wrong?

Thank you, Chris Roy-Smith

here is my code:

#! /usr/bin/python3
from tkinter import *

def NewWindow():
     sw=Toplevel(master)
     sw.title('New Window')
     Label(sw, text='new window').grid(row=0, column=0)
     sframe=Frame(sw, relief=SUNKEN, bg='red').grid(row=1, column=0)
     Label(sframe, text='Label in a frame').grid(row=2, column=0)
     Label(sframe, text='Second label in this frame').grid(row=3, column=0)
     Button(sw, text='close window', command=sw.destroy).grid(row=5, 
column=0)

master=Tk()
master.title('Master Window')
Button(master, text='open window', command=NewWindow).grid(row=1, column=1)
Button(master, text='quit', command=master.destroy).grid(row=2, column=1)
Label(master, text="learning").grid(row=0, column=0)

master.mainloop()