The following lines should make a QT widget appear on the screen, and will
do if run direcly from IDLE or from iPython notebook:

import sys
from PySide import QtGui

app = QtGui.QApplication.instance()
if not app:
    app = QtGui.QApplication(sys.argv)

class Widget(QtGui.QDialog):
    def __init__(self):
        super().__init__()

widget = Widget()
widget.show()

sys.exit(app.exec_())

However if run from EMACS using the default python.el mode, no widget
will pop up on the screen.  This means that many Pyside programs, such
as example programs found at
https://github.com/nicoddemus/PySide-Examples/tree/master/examples when
run from EMACS will produce no response.

If we modify the program to embed a second widget within our main widget,
as below, the widget does pop up on the screen:

import sys
from PySide import QtGui

app = QtGui.QApplication.instance()
if not app:
    app = QtGui.QApplication(sys.argv)

class Widget1(QtGui.QDialog):
    def __init__(self):
        super().__init__()
        widget2 = Widget2()
        widget2.show()
        layout = QtGui.QVBoxLayout()
        layout.addWidget(widget2)
        self.setLayout(layout)

class Widget2(QtGui.QDialog):
    def __init__(self):
        super().__init__()

widget = Widget1()
widget.show()

sys.exit(app.exec_())


This suggests that perhaps in the first example the widget immediately goes
out of scope.

Thanks for any help

Angus M


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