Undo/Redo in PyQt

[Zabin]

Hey!

I am trying to implement the undo and redo facility in pyqt. I have
gone through some sites and was wondering whether iyou always need to
create subclasses and their definitions for the undo/redo action. My
program currently has a single window in which the user enters
information which is used to update a text file as soon as the user
leaves the field- so i essentially need to undo the text in that field
as well as the file. I am puzzled as to how to approach this. Any help
will be much appreciated!

Cheers
Zabin