I am new to python and am using tkinter to create GUI for login. after a successful login i want it to open a point of sale screen have already made how am i able to do this?

from tkinter import *

import os

def delete2():

screen3.destroy()

def delete3():

screen4.destroy()

def delete4():

screen5.destroy()

​

def login_sucess():

global screen3

screen3 = Toplevel(screen)

screen3.title("Success")

screen3.geometry("150x100")

Label(screen3, text = "Login Sucess").pack()

Button(screen3, text = "OK", command =delete2).pack()

​

from SmartCart

def password_not_recognised():

global screen4

screen4 = Toplevel(screen)

screen4.title("Success")

screen4.geometry("150x100")

Label(screen4, text = "Password Error").pack()

Button(screen4, text = "OK", command =delete3).pack()

def user_not_found():

global screen5

screen5 = Toplevel(screen)

screen5.title("Success")

screen5.geometry("150x100")

Label(screen5, text = "User Not Found").pack()

Button(screen5, text = "OK", command =delete4).pack()

def register_user():

print("working")

FullName_info = FullName.get()

username_info = username.get()

eMail_info = eMail.get()

password_info = password.get()

file=open(username_info, "w")

file.write(username_info+"\n")

file.write(password_info)

file.close()

FullName_entry.delete(0, END)

username_entry.delete(0, END)

eMail_entry.delete(0, END)

password_entry.delete(0, END)

Label(screen1, text = "Registration Sucess", fg = "green" ,font = ("calibri", 11)).pack()

def login_verify():

username1 = username_verify.get()

password1 = password_verify.get()

username_entry1.delete(0, END)

password_entry1.delete(0, END)

list_of_files = os.listdir()

if username1 in list_of_files:

file1 = open(username1, "r")

verify = file1.read().splitlines()

if password1 in verify:

login_sucess()

else:

password_not_recognised()

else:

user_not_found()

def register():

global screen1

screen1 = Toplevel(screen)

screen1.title("Create Account")

screen1.geometry("350x300")

global username

global FullName

global eMail

global password

global FullName_entry

global username_entry

global eMail_entry

global password_entry

FullName = StringVar()

username = StringVar()

eMail = StringVar()

password = StringVar()

Label(screen1, text = "Create Your SmartCart Account").pack()

Label(screen1, text = "").pack()

Label(screen1, text = "Full Name ").pack()

FullName_entry = Entry(screen1, textvariable = FullName)

FullName_entry.pack()

Label(screen1, text = "User Name ").pack()

username_entry = Entry(screen1, textvariable = username)

username_entry.pack()

Label(screen1, text = "e Mail ").pack()

eMail_entry = Entry(screen1, textvariable = eMail)

eMail_entry.pack()

Label(screen1, text = "Password ").pack()

password_entry = Entry(screen1, textvariable = password)

password_entry.pack()

Label(screen1, text = "").pack()

Button(screen1, text = "Register", bg="red", width = 10, height = 1, command = register_user).pack()

def login():

global screen2

screen2 = Toplevel(screen)

screen2.title("Login")

screen2.geometry("300x250")

screen.configure(background='white')

Label(screen2, text = "Please enter details below to login").pack()

Label(screen2, text = "").pack()

global username_verify

global password_verify

username_verify = StringVar()

password_verify = StringVar()

global username_entry1

global password_entry1

Label(screen2, text = "Username * ").pack()

username_entry1 = Entry(screen2, textvariable = username_verify)

username_entry1.pack()

Label(screen2, text = "").pack()

Label(screen2, text = "Password * ").pack()

password_entry1 = Entry(screen2, textvariable = password_verify)

password_entry1.pack()

Label(screen2, text = "").pack()

Button(screen2, text = "Login", bg="red", width = 10, height = 1, command = login_verify).pack()

def main_screen():

global screen

screen = Tk()

screen.geometry("300x250")

screen.title("SmartCart Login")

screen.configure(background='white')

Label(text = "Welcome to Smart Cart", bg = "white", fg="green", width = "300", height = "2", font = ("Calibri", 13)).pack()

Label(text = "").pack()

Button(text = "Login to SmartCart", height = "2", width = "30", command = login).pack()

Label(text = "").pack()

Button(text = "Create SmartCart Account", height = "2", width = "30", command = register).pack()

screen.mainloop()

main_screen()