How to SET data source with python?

Discussion created by francescoscalise on Mar 30, 2011
I'm using ArcGIS 9.3.1 with Python 2.5.
I need to change the data source of a lyr file.
I know how to get the data source via comtypes but I still don't find anything on how to set the data source, otherwise to change a data source of a lyr file from a shapefile to another
I also know with ArcGIS 10 we will have the arcpy.mapping module but at this moment I'm still working on 9.3.1.

Thanks anyone for the help.