Uses Arcpy to iterate through all feature classes in a feature dataset to create and populate new fields.

batchFieldUpdate.py

'''
batchFieldUpdate.py

For each feature class in EMST_Districts on Comanche.sde, do the following: 

1 - Adds new field "Feature_Type"
2 - Calculates field
	  if type = null add "vegetation"

'''

import arcpy
from arcpy import *

# Hardcoded path to sde.  Consider creating model with input parameters for reusibility. 
env.workspace = r"C:\Users\RABBEY-C\AppData\Roaming\ESRI\Desktop10.0\ArcCatalog\Comanche.sde\ENV_GIS.ENV_GIS.EMST_Districts"

#For testing locally
#"C:\Users\RABBEY-C\RA_GIS\Projects\RA_EMST\Updated_Phase_Features.gdb\District_Unions"

fcList = ListFeatureClasses()

for fc in fcList:
	print "Updating feature class: %s" % fc
	fieldname = "Feature_Type"
	expression = "getType(!DOT_Type!)"
	codeblock = """def getType(type):
    if type == "ROW":
        return "ROW"
    elif type == "Median":
        return "MEDIAN"
    elif type == "Roadway":
        return "ROADWAY"
    else:
        return 'VEGETATION'"""
	
	AddField_management(fc, fieldname, "TEXT")
	
	CalculateField_management(fc, fieldname, expression, "PYTHON", codeblock)