How do I use push button to trigger a action in PyQt in this code?

Question

I want to use the push butthon('series_search_pushButton') to trigger another window in class Ui_series_search(). Stuck trying to do this.

class Ui_series_search(object):
    def setupUi(self, series_search):
        #codes

    def retranslateUi(self, series_search):
        #codes


class HomePage(object):
    def setupUi(self, MainWindow):
        self.series_search_pushButton = QtGui.QPushButton(self.tab_series)

        self.series_search_pushButton.setObjectName(_fromUtf8("
                               series_search_pushButton"))

    def retranslateUi(self, MainWindow):
        codes


if __name__ == "__main__":
    import sys
    app = QtGui.QApplication(sys.argv)
    MainWindow = QtGui.QMainWindow()
    ui = Homepage()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())