Tkinter skeleton

main.py

from tkinter import Tk, Label, Button

class Main:
    
    APP_NAME = ''
    
    def __init__(self, master):
        self.master = master
        master.title(self.APP_NAME)
        self.center(master)
    
    def center(self, toplevel):
        toplevel.update_idletasks()
        w = toplevel.winfo_screenwidth()
        h = toplevel.winfo_screenheight()
        size = tuple(int(_) for _ in toplevel.geometry().split('+')[0].split('x'))
        x = w/2 - size[0]/2
        y = h/2 - size[1]/2
        toplevel.geometry("%dx%d+%d+%d" % (size + (x, y)))

root = Tk()
root.geometry("600x500")
my_gui = Main(root)
root.mainloop()