import tkinter as tk
from tkinter import * 
my_w = tk.Tk()
my_w.geometry("200x200")  # Size of the window 
my_w.title("www.plus2net.com")  # Adding a title

# create one lebel 
my_str = tk.StringVar()
l1 = tk.Label(my_w,  textvariable=my_str )
l1.grid(row=1,column=2) 
my_str.set("Hi I am main window")
# add one button 
b1 = tk.Button(my_w, text='Clik me to open new window',
               command=lambda:my_open())
b1.grid(row=2,column=2) 

def my_open():
    my_w_child=Toplevel(my_w) # Child window 
    my_w_child.geometry("200x200")  # Size of the window 
    my_w_child.title("www.plus2net.com")
    my_str1 = tk.StringVar()
    l1 = tk.Label(my_w_child,  textvariable=my_str1 )
    l1.grid(row=1,column=2) 
    my_str1.set("Hi I am Child window")
    def my_fun():
        my_w.config(bg='red')
        my_w_child.grab_set()
    b3 = tk.Button(my_w_child, text='Disable parent',
                   command=lambda:my_w_child.grab_set())
    b3.grid(row=2,column=2)
    b4 = tk.Button(my_w_child, text='Enable parent',
                   command=lambda:my_w_child.grab_release())
    b4.grid(row=2,column=3)
my_w.mainloop()