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()