How can I show status of current task running and update the progressbar without freezing at same time in python 2 tkinter?

Question

My code displays a button. When button is pressed, a filedialog appears to ask to user select a file (after a messagebox). No problem here.

My problem occurs when I wan

Answer 1

I create queue for communication with thread

self.queue = Queue.Queue()

and run thread with function which gets queue as parameter.

self.thread = threading.Thread(target=self.my_function, args=(self.queue,))

Thread will run some long-running code and use queue to send messages to main thread.
It will NOT display any message box or change values in widgets.

I ask for file before starting thread - so finally thread doesn't use any tkinter's widget or window.

Main thread uses after() to periodically run function which checks queue and if there is message it gets message and updates Label in window. It also changes value in Progressbar. I use mode="determinate" and don't use progressbar.start().

If message is "TASKS FINISHED" then function doesn't check queue again.

---

Code works as you probably need.

I removed all your comments in code and there are only my comments.

import os

import Tkinter 
import ttk
import tkMessageBox
import tkFileDialog

import threading
import Queue

#import sys
import time


class Tareas():

    def __init__(self, parent, row, column, columnspan):
        self.parent = parent

        self.length=200
        self.value=0
        self.maximum=100
        self.interval=10

        self.barra_progreso = ttk.Progressbar(parent, orient=Tkinter.HORIZONTAL,
                                            length = self.length,
                                           mode="determinate",
                                           value=self.value,
                                           maximum=self.maximum)
        self.barra_progreso.grid(row=row, column=column,
                              columnspan=columnspan)

        self.lbl_estado = Tkinter.Label(parent, text='STATUS:')
        self.lbl_estado.grid(row=9, column=0, padx = 20, pady = 5)

        self.estado_aplicacion = Tkinter.StringVar()
        self.estado_aplicacion.set("Started, waiting for a task...")

        self.lbl_info_estado = Tkinter.Label(parent, text=self.estado_aplicacion.get(), textvariable=self.estado_aplicacion)
        self.lbl_info_estado.grid(row=10, column=0, padx = 20, pady = 5)


    def extraerDatosArchivo(self):
        print 'tarea 1'

        # do some job before you run thread

        self.estado_aplicacion.set('Seleccionando respaldo válido... (1/6)')

        tkMessageBox.showinfo('INFORMACIÓN', 'Select file to decrypt.')

        archivo_respaldo = tkFileDialog.askopenfile(initialdir="/home/furas", title="Select file", filetypes=(("All files", "*.*"), ("All files2", "*.*")) )

        print 'archivo a desencriptar: ', archivo_respaldo

        if archivo_respaldo is None or not archivo_respaldo:
            tkMessageBox.showerror('ERROR', 'No seleccionó nada.')
            return

        # --- (re)set progressbar ---

        # set progressbar for 6+1 steps and `mode="determinate"`.
        # because first step is already done so set value=1
        self.barra_progreso.configure(#mode="indeterminate",
                                      maximum=7,
                                      value=1)

        # don't start progresbar - I will change it manually 
        #self.barra_progreso.start()#self.interval)

        # --- here starts thread ---

        # create queue for communication with thread
        self.queue = Queue.Queue()

        # create thread and send queue as argument
        self.thread = threading.Thread(target=self.my_function, args=(self.queue,))

        # start thread
        self.thread.start()

        # start checking queue    
        self.check_queue()


    def check_queue(self):
        print("check queue")

        # check if something in queue 
        # because `queue.get()` may block program when it waits for message
        if not self.queue.empty():
            # get message from queue
            text = self.queue.get()
            print("get text from queue:", text)

            # change status
            self.estado_aplicacion.set(text)

            # TODO: you can update progressbar
            self.barra_progreso['value'] += 1

            # check if it is last message   
            if text == 'TASKS FINISHED':
                # stop progersbar
                self.barra_progreso.stop()

                #displaying task finished succesfully
                tkMessageBox.showinfo('INFORMATION', 'Done!.')

                # exit without running `root.after()` again
                return

        # check queue after 200ms (0.2s) so mainloop will can do its job
        root.after(200, self.check_queue)


    def my_function(self, queue):

        #CHANGING TASK STATUS
        queue.put('Copiando clave privada... (2/6)')

        #simulating long task
        time.sleep(4)
        print '2'

        #CHANGING TASK STATUS
        queue.put('Creando carpeta de trabajo... (3/6)')

        #simulating long task
        time.sleep(4)
        print '3'

        #CHANGING TASK STATUS
        queue.put('Creando carpeta de trabajo... (4/6)')

        #simulating long task
        time.sleep(4)
        print '4'

        #CHANGING TASK STATUS
        queue.put('Creando carpeta de trabajo... (5/6)')

        #simulating long task
        time.sleep(4)
        print '5'

        #CHANGING TASK STATUS
        queue.put('Creando carpeta de trabajo... (6/6)')

        #simulating long task
        time.sleep(4)
        print '6'

        #CHANGING TASK STATUS
        queue.put('TASKS FINISHED')

class GUI(Tkinter.Frame):
    """ class to define tkinter GUI"""

    def __init__(self, parent,):
        Tkinter.Frame.__init__(self, master=parent)

        tareas = Tareas(parent, row=8, column=0, columnspan=2)

        btn_extraer_datos_archivo = Tkinter.Button(parent, text = 'Select file', width=24, height=2, command=tareas.extraerDatosArchivo, state='normal')
        btn_extraer_datos_archivo.grid(row=2, column=0, padx = 40, pady = 5)

# --- main ---

root = Tkinter.Tk()

root.title('Extractor de datos 1.0')
root.minsize(200, 200)
root.resizable(0,0)

herramienta = GUI(root)
root.mainloop()