Blank tkinter window during long treatment

Question

I'm actually creating a gui for my python program.

The program have to read multiple data from list, using a handler class.

So, this is my __init__, from the SrudbHandler class.

class SrudbHandler:

    def __init__(self, srudb):
        # var
        self.srudbfilepath = srudb
        self.esedb_obj = None
        self.liste_tables = {}
        self.id_table = {}
        # gui
        self.process_window_tk = Tk()
        self.process_window_tk.title('SRUM')
        self.process_window_tk.config(bg='#6ea5d7')
        self.process_window_tk.geometry('450x180')
        self.process_window_tk.resizable(0, 0)
        self.process_window_tk.eval('tk::PlaceWindow . center')
        self.process_window_tk.columnconfigure(0, weight=30)
        self.process_window_tk.columnconfigure(1, weight=30)
        self.frame_process = Frame(self.process_window_tk, bg='#6ea5d7', pady=10, padx=5)
        self.frame_process.pack()
        label_app_resource = Label(self.frame_process, bg='#6ea5d7', text='Application :')
        label_app_timeline = Label(self.frame_process, bg='#6ea5d7', text='Timeline :')
        label_app_resource_process = Label(self.frame_process, bg='#6ea5d7', text='...')
        label_app_timeline_process = Label(self.frame_process, bg='#6ea5d7', text='...')
        self.button_next = Button(self.frame_process, text='Next')
        label_app_resource.grid(row=1, column=0, sticky=W)
        label_app_timeline.grid(row=2, column=0, sticky=W)
        self.label_app_resource_process.grid(row=1, column=1, sticky=W)
        self.label_app_timeline_process.grid(row=2, column=1, sticky=W)
        self.button_next.grid(row=7, column=0, columnspan=2)

Treatment is done later with method of the class. During the treatment, self.label_app_resource_process and self.label_app_timeline_process text is changed from '...' to 'in progress' and then 'done'. But... During the treatment, my window become blank with 'not responding'.

Is this because of the long treatment ('for' loop) ?

Thanks !