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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("250x200")  # Size of the window 
    my_w_child.title("www.plus2net.com")

    l1 = tk.Label(my_w_child,  text='Your Name', width=10 )  # added one Label 
    l1.grid(row=1,column=1) 

    e1 = tk.Entry(my_w_child, width=20,bg='yellow') # added one Entry box
    e1.grid(row=1,column=2)
    b2 = tk.Button(my_w_child, text='Submit',
               command=lambda:my_str.set(e1.get()))
    b2.grid(row=2,column=2) 
    b3 = tk.Button(my_w_child, text=' Close Child',
                   command=my_w_child.destroy)
    b3.grid(row=3,column=2)
    
my_w.mainloop()
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