title: how to use grid positioning in PyQt?
body: <p>I am new to pyqt. I am trying to built a program using QtGui.QMainWindow.</p>
  
  <p>First: is it true that I can't use grid to place object in the parent?</p>
  
  <p>Second: if it is possible , how can I use it?</p>
  
  <p>More specifically, I want to use grid to place widgets in a window which has menu bar.</p>