QThread: Destroyed while thread is still running in Python

Question

I've got this part of code, which sometimes works and sometimes throws warning:
QThread: Destroyed while thread is still running

This part is in UiMainWindow class

obj_thread = QtCore.QThread()

def ok():
    self.module_src_tree.setStyleSheet('background-color: #81F781')
    obj_thread.quit()

def err():
   self.module_src_tree.setStyleSheet('background-color: #F78181')
   obj_thread.quit()

tmp = self.Temp(self, module_revision)
tmp.moveToThread(obj_thread)
tmp.finished.connect(ok)
tmp.error.connect(err)
obj_thread.started.connect(tmp.run)
obj_thread.start()

This is class in UiMainWindow class

class Temp(QtCore.QObject):
    finished = QtCore.pyqtSignal()
    error = QtCore.pyqtSignal()

    def __init__(self, gui, module_revision):
        QtCore.QObject.__init__(self)
        self.gui = gui
        self.module_revision = module_revision

    def run(self):
        try:
            self.gui.dp.pack_module_source(self.gui.module_src_show_list, self.gui.module_src_pack_list,
                                           path=str(self.gui.path_box.text()), revision=self.module_revision)
            self.finished.emit()
        except Exception as e:
            self.error.emit()
            raise e

What I am trying to do with this code - I want to zip some files without freezing main application. So I start new Thread which works in background. But I need functionality that a Widget changes it's color after the zipping is done to green or to red if something went wrong.
Maybe I am doing something wrong? Maybe that is not the way?
Most probles I've got with changing color part.

Best Regards,
Marek

---

@three_pineapples, seeems like it doesn't start at all sometimes. But there is no error/warning right now.
I have modified code to this:

class UiMainWindow(object):
    # thread pool
    thread_pool = [None, None, None, None]

This is before class constructor. Temp class stays the same as above, and Thread calling part of code looks like this right now:

self.thread_pool[3] = None
self.thread_pool[3] = QtCore.QThread()

def ok():
    self.module_src_tree.setStyleSheet('background-color: #81F781')
    self.thread_pool[3].quit()

def err():
    self.module_src_tree.setStyleSheet('background-color: #F78181')
    self.thread_pool[3].quit()

tmp = self.Temp(self, module_revision)
tmp.moveToThread(self.thread_pool[3])
tmp.finished.connect(ok)
tmp.error.connect(err)
self.thread_pool[3].started.connect(tmp.run)
self.thread_pool[3].start()

Answer 1

This issue occurs when the thread is garbage collected by Python.

You need to save a reference to your QThread so it is not garbage collected. Just do self.obj_thread = QtCore.QThread()

If there is the possibility that multiple QThread s will exist at once, and you are storing the references in the same variable, then you probably need to store the objects in a list instead. However, you will need to clear out objects from the list (so they are garbage collected) when a given thread has finished so that you don't introduce a memory leak to your application.