GUI script retornar valor ao ser fechado

Criei um GUI no PAGE para facilitar aprendizado e estou tentando receber valor do FORM quando finalizado. Alguém tem uma solução?

Script base ‘start.py’ onde é iniciado o programa

import sys
import Login

try:
    import Tkinter as tk
except ImportError:
    import tkinter as tk

try:
    import ttk
    py3 = False
except ImportError:
    import tkinter.ttk as ttk
    py3 = True

def init(top, gui, *args, **kwargs):
    global w, top_level, root
    w = gui
    top_level = top
    root = top

def destroy_window():
    # Function which closes the window.
    global top_level
    top_level.destroy()
    top_level = None


if __name__ == '__main__':    
    Login.vp_start_gui()

Aqui o script do FORM ‘Login.py’

import sys
import start

try:
    import Tkinter as tk
except ImportError:
    import tkinter as tk

try:
    import ttk
    py3 = False
except ImportError:
    import tkinter.ttk as ttk
    py3 = True


def vp_start_gui():
    global val, w, root
    root = tk.Tk()
    top = Form_Login (root)
    start.init(root, top)
    root.mainloop()

w = None
def create_Form_Login(rt, *args, **kwargs):
    global w, w_win, root
    #rt = root
    root = rt
    w = tk.Toplevel (root)
    top = Form_Login (w)
    start.init(w, top, *args, **kwargs)
    return (w, top)

def destroy_Form_Login():
    global w
    w.destroy()
    w = None

def buttonLogin(tb_Login):

    if bool(tb_Login.get().strip()):
        #
        #Se entrar, Finaliza e retorna valores
        #
        root.destroy()
    else:
        print ('------------------------------')
        print ('Existem campos não preenchidos')
        print ('------------------------------')



class Form_Login:
    def __init__(self, top=None):
        _bgcolor = '#d9d9d9'  # X11 color: 'gray85'
        _fgcolor = '#000000'  # X11 color: 'black'
        _compcolor = '#d9d9d9' # X11 color: 'gray85'
        _ana1color = '#d9d9d9' # X11 color: 'gray85'
        _ana2color = '#ececec' # Closest X11 color: 'gray92'
        
        top.geometry("300x100")
        top.minsize(120, 1)
        top.maxsize(1924, 1061)
        top.resizable(0,  0)
        top.title("..:: Login ::.. ")
        top.configure(background="#99b4d1")
        top.configure(highlightbackground="#d9d9d9")
        top.configure(highlightcolor="black")
        top.eval('tk::PlaceWindow . center')
        top.attributes('-toolwindow', True)

        self.tb_Login = tk.Entry(top)
        self.tb_Login.place(relx=0.167, rely=0.08, height=20, relwidth=0.813)
        self.tb_Login.configure(background="white")
        self.tb_Login.configure(disabledforeground="#a3a3a3")
        self.tb_Login.configure(font="-family {Helvetica} -size 9")
        self.tb_Login.configure(foreground="#000000")
        self.tb_Login.configure(highlightbackground="#d9d9d9")
        self.tb_Login.configure(highlightcolor="black")
        self.tb_Login.configure(insertbackground="black")
        self.tb_Login.configure(selectbackground="blue")
        self.tb_Login.configure(selectforeground="white")
        self.tb_Login.focus_set()

        self.tb_Pass = tk.Entry(top)
        self.tb_Pass.place(relx=0.167, rely=0.33, height=20, relwidth=0.813)
        self.tb_Pass.configure(background="white")
        self.tb_Pass.configure(disabledforeground="#a3a3a3")
        self.tb_Pass.configure(font="-family {Helvetica} -size 9")
        self.tb_Pass.configure(foreground="#000000")
        self.tb_Pass.configure(highlightbackground="#d9d9d9")
        self.tb_Pass.configure(highlightcolor="black")
        self.tb_Pass.configure(insertbackground="black")
        self.tb_Pass.configure(selectbackground="blue")
        self.tb_Pass.configure(selectforeground="white")

        self.btn_Login = tk.Button(top, command= lambda: buttonLogin(self.tb_Login, self.tb_Pass))
        self.btn_Login.place(relx=0.69, rely=0.6, height=34, width=87)
        self.btn_Login.configure(activebackground="#ececec")
        self.btn_Login.configure(activeforeground="#000000")
        self.btn_Login.configure(background="#d9d9d9")
        self.btn_Login.configure(disabledforeground="#a3a3a3")
        self.btn_Login.configure(foreground="#000000")
        self.btn_Login.configure(highlightbackground="#d9d9d9")
        self.btn_Login.configure(highlightcolor="black")
        self.btn_Login.configure(pady="0")
        self.btn_Login.configure(text='''Login''') 

Removi algumas coisas do Form só pra diminuir o o Script com o necessário, tenho o metodo “buttonLogin” que valida se os campos estão vazios e teria que retornar os valores.
me divirto com c# e resolvi testar o Py, e é uma loucura!