Python3 USES tkinter to implement a simple instance of a UI interface

import time
import tkinter as tk

class Window:
    def __init__(self, title='nms', width=300, height=120, staFunc=bool, stoFunc=bool):
        self.w = width
        self.h = height
        self.stat = True
        self.staFunc = staFunc
        self.stoFunc = stoFunc
        self.staIco = None
        self.stoIco = None

        self.root = tk.Tk(className=title)

    def center(self):
        ws = self.root.winfo_screenwidth()
        hs = self.root.winfo_screenheight()
        x = int( (ws/2) - (self.w/2) )
        y = int( (hs/2) - (self.h/2) )
        self.root.geometry('{}x{}+{}+{}'.format(self.w, self.h, x, y))

    def packBtn(self):
        self.btnSer = tk.Button(self.root, command=self.event, width=15, height=3)
        self.btnSer.pack(padx=20, side='left')
        btnQuit = tk.Button(self.root, text=' Close the window ', command=self.root.quit, width=15, height=3)
        btnQuit.pack(padx=20, side='right')

    def event(self):
        self.btnSer['state'] = 'disabled'
        if self.stat:
            if self.stoFunc():
                self.btnSer['text'] = ' Start the service '
                self.stat = False
                self.root.iconbitmap(self.stoIco)
        else:
            if self.staFunc():
                self.btnSer['text'] = ' Stop the service '
                self.stat = True
                self.root.iconbitmap(self.staIco)
        self.btnSer['state'] = 'active'

    def loop(self):
        self.root.resizable(False, False)   # Window size is not allowed 
        self.packBtn()
        self.center()                       # The window in the middle 
        self.event()
        self.root.mainloop()

########################################################################
def sta():
    print('start.')
    return True
def sto():
    print('stop.')
    return True

if __name__ == '__main__':
    import sys, os

    w = Window(staFunc=sta, stoFunc=sto)
    w.staIco = os.path.join(sys.exec_prefix, 'DLLspyc.ico')
    w.stoIco = os.path.join(sys.exec_prefix, 'DLLspy.ico')
    w.loop()