AttributeError: 'QCoreApplication' object has no attribute 'setQuitOnLastWindowClosed'

I'm getting this error sometimes when I try to quit the Qt event loop. Using a code sample code,

from PyQt5 import QtCore, QtSerialPort

maxcounts = 10
counter = []

app = QtCore.QCoreApplication([]) 

serial_port = QtSerialPort.QSerialPort('COM3')

serial_port.setBaudRate(QtSerialPort.QSerialPort.Baud115200)
serial_port.open(QtCore.QIODevice.ReadWrite) 

serial_port.setDataTerminalReady(1)
serial_port.setDataTerminalReady(0)
serial_port.setDataTerminalReady(1)

def handle_ready_read(): 

    while serial_port.canReadLine():
        resp = serial_port.readLine().data().decode().strip()

        if len(counter) == maxcounts:
            print('closing')
            serial_port.setDataTerminalReady(0)
            serial_port.setDataTerminalReady(1)
            serial_port.setDataTerminalReady(0)
            serial_port.close()
            app.quit() 

        counter.append(1)

        if resp == 'end':
            print('closing')
            serial_port.setDataTerminalReady(0)
            serial_port.setDataTerminalReady(1)
            serial_port.setDataTerminalReady(0)
            serial_port.close()
            app.quit()             

serial_port.readyRead.connect(handle_ready_read) 
 
app.exec_()

Any ideas it would output this error response?

ERROR:tornado.application:Exception in callback functools.partial(<function Kernel.enter_eventloop.<locals>.advance_eventloop at 0x000001DD311F8280>)
Traceback (most recent call last):
  File "C:\Users\me\Anaconda3\lib\site-packages\tornado\ioloop.py", line 741, in _run_callback
    ret = callback()
  File "C:\Users\me\Anaconda3\lib\site-packages\ipykernel\kernelbase.py", line 314, in advance_eventloop
    eventloop(self)
  File "C:\Users\me\Anaconda3\lib\site-packages\ipykernel\eventloops.py", line 131, in loop_qt5
    return loop_qt4(kernel)
  File "C:\Users\me\Anaconda3\lib\site-packages\ipykernel\eventloops.py", line 117, in loop_qt4
    kernel.app.setQuitOnLastWindowClosed(False)
AttributeError: 'QCoreApplication' object has no attribute 'setQuitOnLastWindowClosed'

I'm not using any windows. It doesn't happen every time though, after running once I usually don't see the error again.

Edit: It may be that setting spyder preference ipython console graphics backend as 'automatic' which may use Qt causes this error, instead of setting it as 'inline'. I found that using app = QtWidgets.QApplication([]) with app.setQuitOnLastWindowClosed(True) while commenting out app.quit() let's the plot show while using the automatic setting, without an error.

It seems that you are using some special environment(seems Spyder) where the developer assumes that you are using QGuiApplication or QApplication as an eventloop that have the setQuitOnLastWindowClosed method. A workaround is to create a class that inherits from QCoreApplication and has that method.

class CoreApplication(QtCore.QCoreApplication):
    def setQuitOnLastWindowClosed(self, quit):
        pass


maxcounts = 10
counter = []

app = CoreApplication([])
# ...