Simple_Clock.py

from tkinter import *
from datetime import datetime
import time as pytime # TIP: datetime also contains time so this makes it easier if using both.
from threading import Thread
class TKGUI:
    def __init__(self):
        self.root= Tk() ##initilise the main window
        self.quit = False ##defaults the quit flag
        self.time = "00:00:00"

    def update_time(self): #this just sets the self.time variable to the current time
        self.time = datetime.now().strftime("%H:%M:%S")

    def time_thread(self):  #This will run as a thread
        while not self.quit:
            self.update_time()
            pytime.sleep(0.5) #best to add some form of delay to a thread or it uses too much CPU power to run simple things

    def update_time_lable(self):    #updates the lable
        self.time_L.configure(text=self.time)

    def run(self): ##main part of the application
        self.root.configure(bg="white") #sets the background to white rather than default gray.
        self.root.protocol("WM_DELETE_WINDOW", self.quitting) ##changes the X (close) Button to run a function instead.
        try:
            self.root.iconbitmap("fav.ico") ##sets the application Icon
        except:
            pass
        self.root.title("MyApp")
        self.root.geometry("800x600")
        #############################################################
        #\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\#
        #----------------------Code Goes Here ----------------------#
        #///////////////////////////////////////////////////////////#
        #############################################################
        self.time_L = Label(self.root, text=self.time, bg="white", font=("Courier", 44)) # The label to hold the time
        self.time_L.pack(side=TOP)


        #############################################################
        t=Thread(target=self.time_thread)
        t.start()
        while not self.quit: ##flag to quit the application
            self.root.update_idletasks() #updates the root. same as root.mainloop() but safer and interruptable
            self.root.update() #same as above. This lest you stop the loop or add things to the loop.
            #add extra functions here if you need them to run with the loop#
            if self.time != self.time_L.cget("text"): #adding this for a condition
                self.update_time_lable() #run a function in the mainloop

    def quitting(self): ##to set the quit flag
        self.quit = True

if __name__ == "__main__":
    app = TKGUI() ##creates instance of GUI class
    try:
        app.run()# starts the application
    except KeyboardInterrupt:
        app.quitting() ##safely quits the application when crtl+C is pressed
    except:
        raise #you can change this to be your own error handler if needed