Why does PyQt4 crash ipython-notebook the second time a script is run?

Question

I'm learning PyQt4 right now and made a little script which should open a "Hello World!" box. It works the first time I run it, but the second time, the script does nothing and crashes the ipython-notebook kernal, which requires a restart. I'm using the Spyder IDE in Anaconda, under Windows. This is the code:

import sys
from PyQt4 import Qt,QtGui
a = Qt.QApplication(sys.argv)
a.setActiveWindow(QtGui.QMainWindow())
hello = Qt.QLabel("Hello, World")
hello.show()
a.exec_()

score 1 · Answer 1 · answered Nov 28 '15 at 17:19

Sorry, after a bunch of searching I found a duplicate question: simple IPython example raises exception on sys.exit()

The solution, by Ali B, is to do this:

app = QApplication(sys.argv)
app.aboutToQuit.connect(app.deleteLater)

before calling:

sys.exit(app.exec_())

Why does PyQt4 crash ipython-notebook the second time a script is run?

1 Answers1