pyqt4 - painting outside the paintEvent - disadvantages? -

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pyqt code: correct conclude below code painting outside paintevent? adding graphics object scene same painting ? 

class derivedgraphicsview(qgraphicsview): """graphicsview"""  def __init__(self, parent, name=none): qgraphicsview.__init__(self, parent)  def update(self):     scene = qgraphicsscene(self.parent)     scene.setscenerect(0, 0, scenewidth, sceneheight)     # eg: simple drawing     line = qgraphicslineitem()     scene.additem(line)     line.setpen(pen)     line.setline(x1,y1,x2,y2)     scene.update()     #set view's scene     self.setscene(scene)  def paintevent(self,event): ## logic : reason override paintevent     ....     newevent = qpaintevent(e.region().boundingrect())     qgraphicsview.paintevent(self,newevent)

qt documention mentions should not paint outside paintevent. can please explain drawbacks of above implementation ?


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