QDialog not opening from Main window (pyQt)

Question

I'm trying to launch a dialog by clicking a button in the main window: Here's the (qtdesigner generated) code which I modified just to test it .. I've set the showDial function to show the dial when the button is clicked. But it doesn't work :

from PyQt4 import QtCore, QtGui

try:
    _fromUtf8 = QtCore.QString.fromUtf8
except AttributeError:
    _fromUtf8 = lambda s: s



class Ui_Dialog(object):
    def setupUi(self, Dialog):
        Dialog.setObjectName(_fromUtf8("Dialog"))
        Dialog.setWindowModality(QtCore.Qt.WindowModal)
        Dialog.resize(400, 300)
        Dialog.setWindowTitle(QtGui.QApplication.translate("Dialog", "Dialog", None,   QtGui.QApplication.UnicodeUTF8))

        self.retranslateUi(Dialog)
        QtCore.QMetaObject.connectSlotsByName(Dialog)

    def retranslateUi(self, Dialog):
        pass

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName(_fromUtf8("MainWindow"))
        MainWindow.resize(309, 148)
        MainWindow.setWindowTitle(QtGui.QApplication.translate("MainWindow", "MainWindow", None, QtGui.QApplication.UnicodeUTF8))
        self.centralwidget = QtGui.QWidget(MainWindow)
        self.centralwidget.setObjectName(_fromUtf8("centralwidget"))
        self.pushButton = QtGui.QPushButton(self.centralwidget)
        self.pushButton.setGeometry(QtCore.QRect(50, 30, 191, 71))
        self.pushButton.setText(QtGui.QApplication.translate("MainWindow", "Open Dialog", None, QtGui.QApplication.UnicodeUTF8))
        self.pushButton.setObjectName(_fromUtf8("pushButton"))
        MainWindow.setCentralWidget(self.centralwidget)

        self.retranslateUi(MainWindow)

        QtCore.QObject.connect(self.pushButton, QtCore.SIGNAL(_fromUtf8("clicked(QAbstractButton*)")), self.showDial)

        QtCore.QMetaObject.connectSlotsByName(MainWindow)



    def retranslateUi(self, MainWindow):
        pass

    def showDial(self):
      Dialog = QtGui.QDialog()
      u = Ui_Dialog()
      u.setupUi(Dialog)

      Dialog.exec_()


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

Answer 1

There is error in signal connection, it should be:

QtCore.QObject.connect(self.pushButton, QtCore.SIGNAL(_fromUtf8("clicked()")), self.showDial)

or in more pythonic New-style Signal and Slot syntax for PyQt 4.5+:

self.pushButton.clicked.connect(self.showDial)