PyQt4 + UI Looper

looper.py

#!/usr/bin/env python2
# -*- coding: utf-8 -*-

import Queue
import functools
import itertools
import sys
import threading
import time

from PyQt4 import QtCore
from PyQt4 import QtGui


class Looper(object):

    def __init__(self):
        self.main_id = id(threading.current_thread())
        self.tasks = Queue.Queue()

    def process(self):
        try:
            task = self.tasks.get_nowait()
        except Queue.Empty:
            pass
        else:
            f, args, kw = task
            f(*args, **kw)

    def enqueue_task(self, f, args=None, kw=None):
        task = f, args or [], kw or {}
        self.tasks.put(task)

    def run_in_ui(self, func):

        @functools.wraps(func)
        def wrapper(*args, **kwargs):
            if id(threading.current_thread()) == self.main_id:
                return func(*args, **kwargs)
            else:
                return self.enqueue_task(func, args, kwargs)

        return wrapper


class Top(QtGui.QMainWindow):

    looper = Looper()

    def __init__(self, *args, **kwargs):
        super(Top, self).__init__(*args, **kwargs)

        # Ui
        self.text = None
        self.setup_ui()

        # Timer
        self.timer = QtCore.QTimer()
        self.timer.timeout.connect(self.looper.process)
        self.timer.start(50)

    def setup_ui(self):
        self.text = QtGui.QLineEdit(self)
        self.text.show()

    @looper.run_in_ui
    def set_text(self, text):
        self.text.setText(text)


class Changer(object):

    run = True

    def change(self, w):
        for x in itertools.count():
            if not self.run:
                break
            w.set_text('{}s'.format(x))
            time.sleep(1)

    def stop(self):
        self.run = False


def main():
    app = QtGui.QApplication(sys.argv)

    w = Top()
    w.show()

    changer = Changer()
    app.lastWindowClosed.connect(changer.stop)

    t = threading.Thread(target=changer.change, args=(w,))
    t.start()

    sys.exit(app.exec_())


if __name__ == '__main__':
    main()