title: How do we add a popup window using PyQt?
body: <p>Hi I need to create a pop up window when user clicks a button in the MainWindow.
  So I created a DialogWindow and linked it with MainWindow with below line of code.
  For note I've three modules 1. MainWindow_Ui.py 2. About_Ui.py 3. UiShow.py</p>
  
  <p>Below line of code is included in MainWindow_Ui.py and the module imports &lt; from About_Ui import * >, but still I get the error "global name 'dialog' is not defined". Please suggest. Thanks!</p>
  
  <p><code>QtCore.QObject.connect(self.menuAbout, QtCore.SIGNAL(_fromUtf8("triggered()")), dialog.setupUi(aboutDialog))</code></p>