In the last post, search cursor basics were discussed. When creating search cursors, you can specify many properties, one way to limit the number of row object returned to the end user is the use SQL expressions.
sqlExpression = "\"STATE_NAME\" = 'California'"
fc = r"c:\temp\counties.shp"
rows = arcpy.SearchCursor("C:/Data/Counties.shp", sqlExpression)
# Do stuff with rows
Here only the California counties will be returned.