Animated widgets with only one widget

import sys
from PySide.QtGui import *
from PySide.QtCore import *


class HorizontalAnimator( QWidget ):
    '''A widget where other widgets may slide in or out animated'''

    def __init__(self, parent=None):
        super( HorizontalAnimator, self ).__init__( parent )
        self.widgets = []
        self.visibleWidget = None
        self.end = 0


    def addWidget(self, widget):
        '''Add this widget to the animator, but hide it at the beginning'''

        widget.setParent( self )
        widget.setGeometry(-widget.sizeHint().width(),
                           0,
                           widget.sizeHint().width(),
                           widget.sizeHint().height())
        self.widgets.append( widget )
        widget.hide()

    def change(self, newWidget):
        '''Slide in the new widget and slide out the old one'''

        if not newWidget == self.visibleWidget:
            # Slide in
            newSize = QSize( newWidget.sizeHint().width(), self.height() )
            self.resize( newSize )
            newWidget.show()
            self.animGroup = QParallelAnimationGroup()

            slideInAnimation = self.getMoveAnimation( newWidget,
                                                          -newWidget.sizeHint().width(),
                                                          0 )
            self.animGroup.addAnimation( slideInAnimation )

            # Slide out
            oldWidget = self.visibleWidget
            if oldWidget:
                slideOutAnimation = self.getMoveAnimation( oldWidget,
                                                               0,
                                                               newWidget.sizeHint().width() )
                self.animGroup.addAnimation( slideOutAnimation )
                slideOutAnimation.finished.connect( oldWidget.hide )

            self.animGroup.start()
            self.visibleWidget = newWidget

    def getMoveAnimation(self, widget, start, end):
        '''
        Horizontal animation, moves the widget
        from "start" x-position to "end" x-position.
        '''

        moveAnimation = QPropertyAnimation(widget, 'pos')
        moveAnimation.setDuration(500)
        moveAnimation.setStartValue(QPoint(start, 0))
        moveAnimation.setEndValue(QPoint(end, 0))
        moveAnimation.setEasingCurve(QEasingCurve.OutCubic)
        return moveAnimation


class WidgetPage(QWidget):

    def __init__( self, parent=None ):
        '''Vertical stack of widgets (simulates a column)'''
        super( WidgetPage, self ).__init__( parent )
        self.grid = QVBoxLayout( self )

    def addWidget(self, widget):
        '''Add this widget at the end of the stack'''
        self.grid.addWidget( widget )


class ToolBrowser( QWidget ):
    '''AppStore like panel'''

    def __init__( self, data ):
        super( ToolBrowser, self ).__init__()
        self.data = data
        self.pageDict = {}
        self.initUI()

    def initUI( self ):
        '''Build UI of the MainWindow'''

        # LAYOUT WITH BUTTONS ON LEFT AND ANIMATED PAGE ON RIGHT
        self.setLayout( QHBoxLayout() )
        self.btnLayout = QVBoxLayout()
        self.layout().addLayout( self.btnLayout )
        self.animator = HorizontalAnimator( self )

        # CREATE BUTTONS AND PAGES BASED ON SUPPLIED DATA
        for container in sorted(self.data):
            categoryPage = WidgetPage(self)

            # CREATE CONTAINER BUTTON AND LINK IT TO PAGE
            containerButton = QPushButton(container)
            self.pageDict[containerButton] = categoryPage
            containerButton.clicked.connect(self.pageChangeRequest)
            self.btnLayout.addWidget(containerButton)
            print containerButton.parent()

            # CREATE BUTTONS FOR EACH CATEGORY IN CONTAINER
            for category in self.data[container]:
                categoryPage.addWidget( QPushButton( category ) )

            # ADD PAGE TO ANIMATOR WIDGET
            self.animator.addWidget( categoryPage )

        self.layout().addWidget( self.animator )


        self.resize(350, 400)
        self.setWindowTitle('Tool Browser')

    def pageChangeRequest(self):
        '''The user wants to change the visible page'''

        button = self.sender()
        page = self.pageDict[button]
        self.animator.change(page)

        # or as a one-liner:
        # self.animator.change(self.pageDict[self.sender()])



def main():
    data = dict(
        containerA= (
           dict(CatAA=['A1', 'B1', 'C1'],
                CatAB=['A2', 'B2', 'C2'],
                CatAC=['A3', 'B3', 'C3'])),
        containerB= (
           dict(CatBA=['A4', 'B4', 'C4'],
                CatBB=['A5', 'B5', 'C5'],
                CatBC=['A6', 'B6', 'C6'])),
        containerC= (
           dict(CatCA=['A7', 'B7', 'C7'],
                CatCB=['A8', 'B8', 'C8'],
                CatCC=['A9', 'B9', 'C9'])))

    app = QApplication(sys.argv)
    ex = ToolBrowser( data )
    ex.show()
    sys.exit(app.exec_())


if __name__ == '__main__':
    main()