[PyQt] Confused by this class hierachie ...

[Anon]

Hello Pythoneers,

maybe I am showing here a complete lack of understanding how OOP works or 
at least how Qt works but I have a serious problem with what follows.

Consider the following structure:


file 'widgets.py'
-----------------

- class myMultiLineEdit(QMultiLineEdit)
        o implements a custom context menu, that contains
          an item which should open the dialog (see below)
        
- class widget(QWidget)
        o uses myMultiLineEdit
                        
- class mainWidget(QWidget)
        o uses widget

- class dialog(QDialog)
        o the dialog is modeless (could have been a widget
          as well


file 'ui.py'
------------

- imports 'widgets.py'
- class gui(QMainWindow)
        o uses widgets.mainWidget


file 'start.py'
---------------

- imports 'ui.py'
- creates an instance of ui.gui()


The actual problem now is, that I have not a clue how the dialog could 
operate on the instance created in 'start.py' (My belief is that the dialog 
has to know that instance to call its methods). 

I would be very grateful, if someone could give me an advice how to go on 
with this mess.

Thanks in advance,
Kind regards.