Python PySide (Internal c++ Object Already Deleted

Question

I recently decided to write my first app with Python and PySide. But I have a problem and hope you guys can help.

Python keeps raising exceptions that the "Internal C++ Object" is deleted. From my limited experience with Python I figure that my object is going out of scope and being deleted by Python's Garbage Collector.

So how would I go about designing a multi-page application in Python with PySide. And being able to keep my QWidgets so I can show the page again.

Thanks for your time.

Update (Code)

instancing = None
def instance():
   global instancing
   if instancing == None:
      instancing = WPZKernel()
   return instancing

class WPZKernel:
    win = None
    mainscreen = None

    def mainwindow(self):
        if self.win == None:
          self.win = GMKMainWindow(self)
        return self.win

    def main_panel(self):
        if self.mainscreen == None:
           self.mainscreen = GMKMainScreen(self.mainwindow())
        return self.mainscreen

I would then normally access the mainpanel by calling:

import kernel
kernel.instance().main_panel()

So am I going about this the wrong way?

Answer 1

After some searching and hair pulling, I found the solution. I was showing all the pages by setting them as the central widget, and when reading the QMainWindow documentation I found that my widget basically gets deleted by qt as stated:

Note: QMainWindow takes ownership of the widget pointer and deletes it at the appropriate time.

So to develop a Multi-Page application rather take a look at QStackedWidget.

Answer 2

See here: PySide Pitfalls.

If a QObject falls out of scope in Python, it will get deleted. You have to take care of keeping a reference to the object:

• Store it as an attribute of an object you keep around, e.g. self.window = QMainWindow()
• Pass a parent QObject to the object’s constructor, so it gets owned by the parent