[Python] How to implement a GUI that works with threads?

I've been working on a download manager that automatically opens a GUI menu whenever a new file is downloaded, allowing me to specify a save location.

Currently, I use the following Python script to detect new downloads and trigger the menu:

from watchdog.observers import Observer
import time
from globals import DOWNLOADS_FOLDER
import os
import threading
import menu
from collections import deque

TEMP_FILE_EXTENSIONS = {'.tmp', '.crdownload', '.download', '.part', '.swp', '.temp'}

class DownloadHandler(FileSystemEventHandler):
def __init__(self):
"""Initialize the handler."""
self.open_threads = True
self.events_to_handle = deque()
self.menu_thread_lock = threading.Lock()
self.menu_thread = threading.Thread(target=self.loop_through_menus, daemon=True)
self.menu_thread.start()

def on_created(self, event: FileSystemEvent):
"""Handle file created events."""
file_path = event.src_path
self.events_to_handle.append(file_path)

def on_moved(self, event: FileSystemEvent):
"""Handle file moved events."""
original_path = event.src_path
file_path = event.dest_path

if self.is_download_folder(original_path) and file_path.endswith(tuple(TEMP_FILE_EXTENSIONS)):
self.events_to_handle.append(file_path)

def loop_through_menus(self):
"""Loop through events and handle them."""
while self.open_threads:
if self.events_to_handle:
with self.menu_thread_lock: # Ensure thread safety when modifying the deque
file_path = self.events_to_handle.popleft()
self.new_download_file(file_path)
else:
time.sleep(0.1)

def new_download_file(self, file_path):
"""Check if the file is in Downloads and move it if not temporary."""
if self.is_download_folder(file_path):
if not file_path.endswith(tuple(TEMP_FILE_EXTENSIONS)) and not os.path.basename(file_path).startswith("."):
print(file_path)
self.create_and_run_menu(file_path)

def create_and_run_menu(self, file_path):
"""Create and run the file move menu."""
menu.run(file_path)

def is_download_folder(self, file_path):
"""Check if the file is in the Downloads folder."""
return os.path.dirname(file_path) == DOWNLOADS_FOLDER

def close_thread(self):
"""Gracefully stop the background thread."""
self.open_threads = False
self.menu_thread.join()

if __name__ == "__main__":
event_handler = DownloadHandler()
observer = Observer()

# Set observer to monitor the Downloads folder (use absolute path if needed)
observer.schedule(event_handler, DOWNLOADS_FOLDER, recursive=True)
observer.start()

try:
while True:
time.sleep(1)
finally:
observer.stop()
observer.join()
event_handler.close_thread()


However, I've encountered an issue: Most Python GUI frameworks don't work well with threads. I've tried both PyQt6 and Tkinter, but neither worked. Instead, I get the following error:

libc++abi: terminating due to uncaught exception of type NSException
​

Since threading seems to be an issue, I’m looking for alternative solutions: Are there any lightweight GUI frameworks that handle this better? Any way to handle my current implementation without using threading?

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