import tkinter as tk from threading import Thread import datetime import time class SampleApp(tk.Tk): def __init__(self): tk.Tk.__init__(self) # Make a StringVar that will contain the value self.value = tk.StringVar() # Make a label that will show the value of self.value self.label = tk.Label(self, textvariable=self.value).pack() # Make a thread that will run outside the tkinter program self.thread = Thread(target=self.show_time) # set daemon to True (This means that the thread will stop when you stop the tkinter program) self.thread.daemon = True # start the thread self.thread.start() tk.Button(self, text="Click me", command=lambda: print("Hello World")).pack() def show_time(self): # The thread will execute this function in the background, so you need to while loop to update the value of self.value while True: # Get the time (in your case, you need to get the api data) data = datetime.datetime.now().strftime('Time: %H:%M:%S, Milliseconds: %f') # Update the StringVar variable self.value.set(data) # Pause the while loop with 1 second, so you can set an interval to update your value time.sleep(1) # rest of your code. root = SampleApp() root.mainloop()