Python kernel dies for second run of PyQt5 GUI

Question

• Using Spyder in Python 3.5.2 |Anaconda 4.2.0 (64-bit) Windows package. qt: 5.6.0
• For first run, GUI window opens as expected
• For 2nd run, nothing opens, and receiving Kernel died, restarting log message.

gui1.py:

import sys from PyQt5.QtWidgets import QApplication, QWidget

app = QApplication(sys.argv)

w = QWidget()

w.resize(250,150) w.show()

#sys.exit(app.exec_()) 
app.exec_()

IPhython log:

runfile('F:/work/ws_python/TestProj1/gui1/gui1.py', wdir='F:/work/ws_python/TestProj1/gui1')

runfile('F:/work/ws_python/TestProj1/gui1/gui1.py', wdir='F:/work/ws_python/TestProj1/gui1')

Kernel died, restarting

Kernel died, restarting

Kernel died, restarting

Why kernel dies for 2nd run and how to solve it?

(Doing the same even using #sys.exit(app.exec_()) as last line.)

Answer 1

This code fixed the problem, thanks for the hint.

app = QtCore.QCoreApplication.instance()
if app is None:
    app = QtWidgets.QApplication(sys.argv)

Answer 2

This works better for the kernel died, restarting error.

from PyQt5.QtWidgets import QApplication, QDialog
from PyQt5.QtCore import QCoreApplication

#app = QApplication(sys.argv)
app = QCoreApplication.instance()
if app is None:
    app = QApplication(sys.argv)