main.py

#!/usr/bin/python3

import tkinter as tk
import os

class Application(tk.Frame):
 def __init__(self, master=None):
 super().__init__(master)
 self.master = master
 self.pack()
 self.create_widgets()

 def create_widgets(self):
 w = tk.Label(self.master, text="hello")
 w.pack()

root = tk.Tk()
app = Application(master=root)
app.mainloop()