python - How to update the progress bar value in a tkinter window from a Flask application which is in another thread?

Question

I have a Flask application that inserts some data in a database. While the insertion is in progress, I want a progress bar to show how many data were inserted (so, I use the determinate mode). Knowing that Flask and tkinter do not go together well proof, I decided to show the tkinter window in a separate thread, the main thread being the Flask application.

Here is my code so far

import tkinter as tk
from multiprocessing import Process
from tkinter.ttk import Progressbar, Button

import global_library
from application import config
from application.admin import add_match as a
from application.xml import create_string as cs
from application.xml import dl_xml_file as dl
from application.xml import xml_parsing as xp

def show_progress_window(low_end, high_end, match_count):
    root = tk.Tk()
    progress_bar = Progressbar(root, mode='determinate', orient='horizontal', length=200)
    progress_bar['maximum'] = high_end - low_end
    progress_bar['value'] = match_count
    progress_bar.pack()
    cancel_button = Button(root, text='Anulare')
    cancel_button.pack()
    root.mainloop()


def import_engine(low_end, high_end):
    file = config['DEFAULT']['PROTECTED_RESOURCE_PATH']
    for match_id in range(low_end, high_end + 1, 1):
        p = Process(target=show_progress_window, args=(low_end, high_end, match_id - low_end))
        p.start()
        p.join()
        params = cs.create_match_details_string(match_id)
        dl.download_xml_file(file, params, global_library.details_savepath)
        match_details = xp.parse_match_details_file(match_id)
        a.add_a_match(match_details[0], match_details[1], match_details[2], match_details[3], match_details[4],
                      match_details[5], match_details[6], match_details[7], match_details[8], match_details[9],
                      match_details[10], match_details[11], match_details[12], match_details[13], match_details[14],
                      match_details[15], match_details[16])

When I run this part, the progress bar updates, but I have to manually close the window for the importing to begin. After each import, the window appears, with the progress bar showing... progress. Obviously, this is from mainloop(). As obvious, I cannot suppres this method.

Where am I mistaking? What should I do so as I don't have to manually close the window at each iteration?

Later edit: a very important fact is that tkinter must run in the main thread. If it doesn't, the progress bar will not update no matter what.

标签： pythonmultithreadingflasktkintermultiprocessing

Answer 1

Okay, my first answer made no sense. Have you tried taking the mainloop out of the function. Because now each time you call on the progress bar, it creates a new tk() instance.

something lke this:

root = tkinter.Tk()
# call your function and pass "root" to it as well
root.mainloop()

Edit 1: The code below provides two functions illustrating that it seems you can 'update' tkinter by starting a new mainloop. But that's not the case.

import tkinter as tk

def looptk(min,max,progress):
    root=tk.Tk()
    label = tk.Label(root, text=progress).pack()
    root.mainloop()
    print(id(root))


def looptk2(min,max,progress,root):
    label = tk.Label(root, text=progress).pack()
    print(id(root))

min = 0
max = 6
i = 0

while i < max:
    looptk(1,5,i)
    i += 1

root=tk.Tk()
min = 0
max = 6
i = 0
while i < max:
    looptk2(1,5,i,root)
    i += 1
root.mainloop()

Edit 2:

Here is where you call the mainloop several times:

for match_id in range(low_end, high_end + 1, 1):
        p = Process(target=show_progress_window, args=(low_end, high_end, match_id - low_end))

To fix it you need to create a mainloop before that for loop. Change it to something like this:

root = tk.tk()
for match_id in range(low_end, high_end + 1, 1):
    p = Process(target=show_progress_window, args=(low_end, high_end, match_id - low_end,root))

root.mainloop()

Don't forget to add "root" between the brackets of the function show_progress_window(Add root to the end). And remove the mainloop from the function.