Updating data with Python

Hello,

I have a problem I can not find a solution. I started few months in Python.

I am looking for a python script allowing me to perform an update of data.

My table has a field "TextString" which actually contains abbreviations.
I created a new field to specify the full name, "FULL_NAME". I complete this field manually.

When I receive a new table with updated data, I can compare my two tables with this script:

import arcpy
set_one = set (r [0] for r in arcpy.da.SearchCursor ("Table1", "Fields"))
set_two = set (r [0] for r in arcpy.da.SearchCursor ("Table2", "Fields"))
print "Set1 Set2 difference: {0}" format (set_two.difference (set_one)).

From this point I know the new data.

But how do I get the field "FULL_NAME" and so to match my new updated table?

Thank you for your help