PyQt Base with ui file

from PyQt4 import QtGui, QtCore, uic
import maya.cmds as cmds
import sip, os

uiFile = os.path.join(os.path.dirname(__file__), "designer_selectWindow_2.ui")

windowTitle = "Scene Manip"
windowObject = "pySceneManipWin"

def getMainWindow():
    import maya.OpenMayaUI as mui
    pointer = mui.MQtUtil.mainWindow()
    return sip.wrapinstance(long(pointer), QtCore.QObject)


class SceneManipWin(QtGui.QMainWindow):
    def __init__(self, parent=None):
        super(SceneManipWin, self).__init__(parent)

        #Loads the contents of the UI file into self
        uic.loadUi(uiFile, self)

        #Sets the window title
        self.setObjectName(windowObject)
        self.setWindowTitle(windowTitle)

        self.mainWidget = QtGui.QWidget()
        self.setCentralWidget(self.mainWidget)
        self.mainWidget.setLayout(self.mainGrid)#mainGrid is in the ui file


def mayaRun():
    if cmds.window(windowObject, q=True, exists=True):
        cmds.deleteUI(windowObject)
    global gui
    gui = SceneManipWin(getMainWindow())
    gui.show()

mayaRun()