When running code the dialogues of the program do not show.

I Know this is probably a silly question, but being very new to python and having hunted for a decent IDE before finding PyCharm, which seems great by the way, I just cant get my forms to show when running the code through PyCharm. I receive no error messages etc, so am pretty sure the code is fine. Also when I run the code through IDLE the program works fine. I am sure it si simply my ignorance of PyCharm, but would appreciate being pointed in the right direction.

Thanks

here is the code by the way

The Diag class

from PySide import QtCore, QtGui

class Ui_Dialog(object):
    def setupUi(self, Dialog):
        Dialog.setObjectName("Dialog")
        Dialog.resize(400, 300)
        self.pushButton = QtGui.QPushButton(Dialog)
        self.pushButton.setGeometry(QtCore.QRect(110, 80, 75, 23))
        self.pushButton.setObjectName("pushButton")

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

    def retranslateUi(self, Dialog):
        Dialog.setWindowTitle(QtGui.QApplication.translate("Dialog", "Dialog", None, QtGui.QApplication.UnicodeUTF8))
        self.pushButton.setText(QtGui.QApplication.translate("Dialog", "testbtn", None, QtGui.QApplication.UnicodeUTF8))

and then the calling code:

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

class MainDialog(QDialog,diagtest.Ui_Dialog):

    def __init(self,parent=None):
        super(MainDialog,self).__init__(parent)
        self.setupUi(self)


app = QApplication(sys.argv)
frm = MainDialog()
frm.show()

app.exec_()