Arcpy class is new to ArcGIS 10.0. ArcPy is a site-package that builds on (and is a successor to) the successful arcgisscripting module. Its goal is to create the cornerstone for a useful and productive way to perform geographic data analysis, data conversion, data management, and map automation with Python. Here's a code that will add a new field to a shapefile and then specify the contents of the added field. In this case, all areas greater than 1000 square meters will be labelled "YES" meaning it is subdividable otherwise it will be "NOO". ********************************************************************************** import arcpy def cursor(): inFeatures = GetParameterAsText(0) subdvdable = GetParameterAsText(1) #inFeatures = "C:\\Users\\RS Lab\\Desktop\\222\\vector\\parcel_area.shp" arcpy.AddField_management(inFeatures, subdvdable, "TEXT") rows = arcpy.UpdateCursor(inFeatures) for row in rows: