Singleton, QApp

 
from pyqtgraph.Qt import QtGui, QtCore
import pyqtgraph as pg

class Application( object):
    __instance = None

    @staticmethod
    def getInstance():
        """ Static access method. """
        if Application.__instance == None:
            Application()
        return Application.__instance 

    def __init__(self):
        if Application.__instance != None:
            raise Exception("Application class is a singleton!")
        else:
            Application.__instance = self    
            self.QApp = QtGui.QApplication.instance()
            if self.QApp is None:
                pg.setConfigOption( 'background', 'w')
                pg.setConfigOption( 'foreground', 'k')
                self.QApp = pg.mkQApp()

app = Application.getInstance()