How to spawn thread and initialize Qt Application in Python with Mac OSX

Question

I am currently having trouble trying to spawn a thread in python while initiating my qt application. The idea in this code is to spawn a python thread that will loop on a function and then initialize my QT application.

import sys 
from PyQt4 import QtGui
from pyui import DirectGui
from engines import KCluster_Engine
from threading import Thread

def main():

    app = QtGui.QApplication(sys.argv)
    dgui = DirectGui()
    engine = KCluster_Engine(4, 5)
    dgui.set_engine_ref(engine)
    engine.assign_interface(dgui)
    thread = Thread(target = engine.start())
    thread.start()
    sys.exit(app.exec_())
    thread.join()

if __name__ == '__main__':
    main()

The problem behind this is that I cannot use my Qt GUI. My mac gives me a color wheel indicating that my thread that I spawned is spinning, which its supposed to do, but I cannot use my QtApplication.

My thread is spinning on purpose in a while loop, its only supposed to trigger after certain actions on the GUI have been done, but I can't interact with my GUI as the mac color wheel (spinning beachball of death) is preventing me to do so.

But Imagine a mac color wheel cursor (spinning beachball of death) also, screenshot doesn't capture it.

Answer 1

This is happening because you're doing this:

thread = Thread(target = engine.start())

When you really want this:

thread = Thread(target=engine.start)

You're accidentally calling engine.start() in your main thread, so your program is getting stuck in the infinite loop that runs in that method.