# -*- coding: cp1251 -*-

from PyQt4 import QtGui, QtCore
import sys

class MainWindow(QtGui.QMainWindow):
    def __init__(self, parent):
        QtGui.QMainWindow.__init__(self, parent)
        # Создание виджетов
        self.widget1 = QtGui.QWidget(self)
        # Установка фонового цвета
        self.widget1.setAutoFillBackground(True)
        p1 = QtGui.QPalette()
        p1.setColor(QtGui.QPalette.Background, QtCore.Qt.green)
        self.widget1.setPalette(p1)
        self.widget1.hide()
        
        self.widget2 = QtGui.QWidget(self)
        self.widget2.setAutoFillBackground(True)
        p2 = QtGui.QPalette()
        p2.setColor(QtGui.QPalette.Background, QtCore.Qt.black)
        self.widget2.setPalette(p2)
        self.widget2.hide()
        # Тулбар
        self.toolbar = QtGui.QToolBar(self)
        self.actionW1 = QtGui.QAction(u'widget1', self)
        QtCore.QObject.connect(self.actionW1, QtCore.SIGNAL("triggered()"), self.changeWidget)
        self.actionW2 = QtGui.QAction(u'widget2', self)
        QtCore.QObject.connect(self.actionW2, QtCore.SIGNAL("triggered()"), self.changeWidget)
        self.toolbar.addAction(self.actionW1)
        self.toolbar.addAction(self.actionW2)
        self.addToolBar(self.toolbar)
        
    def changeWidget(self):
        sender = self.sender()
        # Сначала скрываем оба виджета
        for obj in [self.widget1, self.widget2]:
            obj.hide()
        if sender is self.actionW1:
            self.setCentralWidget(self.widget1)
            self.widget1.show()
        elif sender is self.actionW2:
            self.setCentralWidget(self.widget2)
            self.widget2.show()

if __name__=='__main__':
    app=QtGui.QApplication(sys.argv)
    wg=MainWindow(None)
    wg.show()
    app.exec_()