Progress Bar - Tkinter

To update the progress bar, associate a tkinter variable in it:

import tkinter as t
from tkinter import ttk

root = t.Tk()

.... # codigo definindo o resto da interface ...

var_barra = t.DoubleVar()
minha_barra = ttk.Progressbar(root, variable=var_barra, maximum=30)

Then just update this variable from time to time, and call root.update() to update on the screen!

var_barra.set(k) # k é um número entre 0 e o máximo 
                 # (definido como 30 no exemplo acima)
root.update()

Time and right way to call these functions depends on the processing you are doing! In general, you can use root.after() to call a function multiple times automatically.