如何使用线程自动关闭PyQt / PySide窗口？

Question

How can I make a PyQt5 window automatically close after 30 seconds and still keep the window respond to interaction?

I'm creating a thread which sleeps for 30 seconds, and then it calls the close() function of the window. Right now, the code hangs at self.close() :

Exception in thread Thread-1:
Traceback (most recent call last):
  File "C:\Users\fredrik\.conda\envs\pysidedev_py27\lib\threading.py", line 801, in __bootstrap_inner
    self.run()
  File "C:\Users\fredrik\.conda\envs\pysidedev_py27\lib\threading.py", line 754, in run
    self.__target(*self.__args, **self.__kwargs)
  File "C:\Users\fredrik\Desktop\timer.py", line 47, in <lambda>
    my_win.execute_function_threaded(func=lambda: my_win.auto_close(n=3))
  File "C:\Users\fredrik\Desktop\timer.py", line 36, in auto_close
    self.close()  # hangs
RuntimeError: Internal C++ object (MyWindow) already deleted.

I also tried moving the threading out of the window object but then I'm still experiencing a hang on window.close() .

What am I doing wrong?

The code must work with Python 2.7 and 3.5.

import sys
import time
from threading import Thread

try:
    from PyQt5 import QtWidgets
except ImportError:
    try:
        from PySide2 import QtWidgets
    except ImportError:
        try:
            from PyQt4 import QtGui as QtWidgets
        except ImportError:
            try:
                from PySide import QtGui as QtWidgets
            except ImportError:
                print('giving up!')


class MyWindow(QtWidgets.QMainWindow):
    """Auto-closing window"""
    def __init__(self, parent=None):
        super(MyWindow, self).__init__(parent)

    def closeEvent(self, event):
        """Delete object when closed"""
        self.deleteLater()

    def auto_close(self, n):
        """Close self in n seconds"""
        print('going to sleep')
        for i in range(n):
            print('sleeping...')
            time.sleep(1)
        print('done sleeping!')
        self.close()  # hangs

    def execute_function_threaded(self, func):
        """Run given function in thread"""
        self.t = Thread(target=func)
        self.t.start()
        print('thread started')

app = QtWidgets.QApplication(sys.argv)
my_win = MyWindow()
my_win.show()
my_win.execute_function_threaded(func=lambda: my_win.auto_close(n=3))
sys.exit(app.exec_())

Please note that the Qt binding imports are just done like that in order to make this code run easier on your end ;)

Answer 1

Try following code instead of my_win.execute_function_threaded call:

class MyWindow(QtWidgets.QMainWindow):
    """Auto-closing window"""
    def __init__(self, parent=None):
        super(MyWindow, self).__init__(parent)
        QtCore.QTimer.singleShot(30000, self.close)

Answer 2

The reason the original code doesn't work is because you are forbidden to call Qt GUI methods from secondary threads (Qt methods are not thread safe). There are several solutions to this, such as:

• using a QTimer (since QTimer doesn't use threads, and just queues up a future event in the Qt event loop that exists in the main thread, this solution should solve the segfaults - see the answer by @ingvar )

• using a QThread and a custom Qt signal. Qt signals are thread safe, so you can connect a signal in a secondary thread to the close slot in the primary thread. Then you can emit the signal from within the secondary thread after 30 seconds to trigger the close.

The approach you should take depends on your end goal (and how much of a 'toy' example this is), but for now I see no reason to have a secondary thread. You should just go with @ingvar's answer :)

PS Either way, using python threads with Qt is a bad idea. Stick to QThread unless the thread is completely independent of the GUI.