[PyQt] GraphicsItem, QObject Inheritance problem

Jason H scorp1us at yahoo.com
Thu Oct 1 19:10:20 BST 2009

I think you and I are very close to a nice work-around. I see you're providing a object as a property, and connecting to that. 
What I think should be possible, is to provide a QObject derived class (on the outside), then using __getattr__(self, name), __setattr__(self, name, value), and maybe __call__(self, args) and be able to transparently proxy them to the non-QObject object on the inside. 

It isn't true inheritance, but it would get the job done. Is there anything like this already?

From: Brian Kelley <kelley at eyesopen.com>
To: Jason H <scorp1us at yahoo.com>
Cc: "pyqt at riverbankcomputing.com" <pyqt at riverbankcomputing.com>
Sent: Thursday, October 1, 2009 10:34:59 AM
Subject: Re: [PyQt] GraphicsItem, QObject Inheritance problem

Re: [PyQt] GraphicsItem, QObject Inheritance problem All you need to connect signals and slots is a qobject.  You can create any qobject for this task.

Here is a concrete example, actually using a QGraphicsItem.  This makes an Image button that emits a signal “clicked()” and move the graphics to mimic a button press:

class ImageButton(QtGui.QGraphicsPixmapItem):
    def __init__(self, pixmap, parent=None, oneshot=True):
        QtGui.QGraphicsPixmapItem.__init__( self, pixmap, parent )
        self.emitter = QtCore.QObject()
        self.oneshot = oneshot
        self.callback = None
    def mousePressEvent(self, event):
          self.emitter.emit( QtCore.SIGNAL("clicked()") )
          if self.callback:

    def mouseReleaseEvent(self, event):
        if not self.oneshot:

To connect to this signal as follows:

foo = ImageButton(...)
foo.emitter.connect( foo.emitter, QtCore.SIGNAL(“clicked()”), pythonfunc )

I find this to be cleaner than wrapping a QObject around the graphics item, but in internet speak YMMV.



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