[Python] How can I run a long-running task in Tkinter without freezing the UI (while keeping...

I’m building a Tkinter app where I visualize sorting algorithms on a Canvas. The problem: whenever I run the sorting function, the entire UI freezes until the function finishes.

Here’s a simplified version of my code:

import tkinter as tk
import time

def bubble_sort(canvas, data):
n = len(data)
for i in range(n):
for j in range(0, n-i-1):
if data[j] > data[j+1]:
data[j], data[j+1] = data[j+1], data[j]
draw_data(canvas, data)
time.sleep(0.1) # <-- freezes the UI

def draw_data(canvas, data):
canvas.delete("all")
for i, val in enumerate(data):
canvas.create_rectangle(i*20, 200-val, (i+1)*20, 200, fill="blue")

def start_sort():
bubble_sort(canvas, [5,3,8,4,2])

root = tk.Tk()
canvas = tk.Canvas(root, width=200, height=200)
canvas.pack()

btn = tk.Button(root, text="Start", command=start_sort)
btn.pack()

root.mainloop()


Issues I face:

The UI freezes during sorting, and I can’t interact with the window.

If I try after() instead of sleep, I get confused about how to rewrite the nested loops.

I’ve seen people suggest using threads, but then I run into errors when updating the Canvas from a thread (since Tkinter isn’t thread-safe).

What’s the best practice in Tkinter for running long tasks (like sorting) while keeping the GUI responsive?

Should I restructure the algorithm to work with after() instead of sleep?

Or is it better to use threads/processes with some kind of queue to update the Canvas?

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