title: PySide edit widget from another class
body: <p>I'm having trouble with a program that I'm writing.  As its going to be quite large, I want to separate the layouts and signals, etc into separate classes/modules to make things easier to read.  I would like to be able to edit the layout widgets from another class.  Is this possible, or am I trying to do something that is not possible?  I've included an example below, in case my explanation is not clear</p>
  
  <pre><code>class Layout:
    def __init__(self):
      self.callback = CallBack()
  
    def Gui(self):
      ''' 
      some layout with a listwidget that affects another listwidget depending on choice for example
      '''
      self.list1 = QtGui.QListWidget()
      self.list1.addItems(['chocolate', 'candy', 'pop'])
  
      self.list1.itemClicked.connect(self.callback.ButtonCallback)
  
      self.list2 = QtGui.QListWidget()
  
  class CallBack(Layout):
    def __init__(self)
      super(CallBack, self).__init__()
  
    def ButtonCallback(self, button_signal):
      '''
      do get options for self.list2 depending on chosen item
      '''
  
      new_items = ['item1', 'item2', 'item3']
      Layout.list2.addItems(new_items)
  </code></pre>
  
  <p>I realize that the last line of the code is probably wrong but that is the part that I'm struggling with.</p>
  
  <p>Many thanks for any help.</p>