How to Prevent Tkinter GUI Freezing While Waiting for Threads to Complete?

Freezing/Hanging Tkinter GUI While Waiting for Threads to Complete

When a button on a tkinter GUI is pressed, it often results in the interface freezing. Despite utilizing threading, the issue persists. By leveraging advice from the Python Cookbook, here's a solution to maintain GUI responsiveness while executing an asynchronous task:

Avoid Blocking the Main Thread

The main culprit behind GUI freezing is the utilization of join() on a background thread. To prevent this, a better approach is to implement a "polling" mechanism.

Polling Mechanism

Tkinter's universal after() method enables continuous monitoring of a Queue at regular intervals. This allows the GUI to remain responsive while waiting for thread completion.

Implementation Example

The following code exemplifies this approach:

<code class="python">import Tkinter as tk
import threading
import queue

# Create a queue for communication
queue = queue.Queue()

# Define the GUI portion
class GuiPart(object):
    def __init__(self, master, queue):
        # Set up the GUI
        tk.Button(master, text='Done', command=self.end_command).pack()

    def processIncoming(self):
        while not queue.empty():
            # Handle incoming messages here

    def end_command(self):
        # Perform necessary cleanup and exit

# Define the threaded client
class ThreadedClient(object):
    def __init__(self, master):
        # Set up GUI and thread
        self.gui = GuiPart(master, queue)
        self.thread = threading.Thread(target=self.worker_thread)
        self.thread.start()

        # Start periodic checking of the queue
        self.periodic_call()

    def periodic_call(self):
        self.gui.processIncoming()
        master.after(200, self.periodic_call)

    def worker_thread(self):
        # Perform asynchronous I/O tasks here, adding messages to the queue

# Main program
root = tk.Tk()
client = ThreadedClient(root)
root.mainloop()</code>

In this example, the communication between the GUI and a background thread is handled through a queue, allowing for asynchronous execution without freezing the GUI.

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