python - From where comes the parent argument (PySide)? -

in example, comes parent argument, provides it?

class mainwindow(qtgui.qmainwindow):     def __init__(self):         super(mainwindow, self).__init__()          self.do_something() #sanity check         self.cw = childwidget(self)         self.setcentralwidget(self.cw)         self.show()      def do_something(self):         print 'doing something!'   class childwidget(qtgui.qwidget):     def __init__(self, parent):         super(childwidget, self).__init__(parent)          self.button1 = qtgui.qpushbutton()         self.button1.clicked.connect(self.do_something_else)          self.button2 = qtgui.qpushbutton()         self.button2.clicked.connect(self.parent().do_something)          self.layout = qtgui.qvboxlayout()         self.layout.addwidget(self.button1)         self.layout.addwidget(self.button2)         self.setlayout(self.layout)         self.show()      def do_something_else(self):         print 'doing else!' 

parent , children specific qt (c++). doc of qobject:

qobjects organize in object trees. when create qobject object parent, object automatically add parent's children() list. parent takes ownership of object; i.e., automatically delete children in destructor.

qwidget , lot of other class inherits fromqobject, apply them too. every children, parent() method returns pointer parent object.

basically, creates widget parents can deleted properly. common case, main window parent - or grandparent - of widgets: when close window, deleted in right order.

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from comment, think confused use ofsuper(). not call parent of widget.

another way write this:

class childwidget(qtgui.qwidget):     def __init__(self, parent):         super(childwidget, self).__init__(parent) 

is call init method of qwidget directly:

class childwidget(qtgui.qwidget):     def __init__(self, parent):         qtgui.qwidget.__init__(parent) 

childwidget inherits qwidget (that's how defined class). in init method, need call default constructor of qwidget. otherwise won't able use default methods , attributes of qwidget (try , see...).
if given parent, organize accordingly. add parent children method, , keep reference parent.