The following script uses the AssignDomainToField function as part of a workflow to create an attribute domain, assign values to the domain, and assign the domain to a field.
# Name: MakeDomain.py
# Description: Create an attribute domain to constrain pipe material values
# Import system modules
import arcpy
# Set the workspace (to avoid having to type in the full path to the data every time)
arcpy.env.workspace = "C:/data"
# Set local parameters
domName = "Material4"
gdb = "montgomery.gdb"
inFeatures = "Montgomery.gdb/Water/Distribmains"
inField = "Material"
# Process: Create the coded value domain
arcpy.CreateDomain_management("montgomery.gdb", domName, "Valid pipe materials",
"TEXT", "CODED")
# Store all the domain values in a dictionary with the domain code as the "key"
# and the domain description as the "value" (domDict[code])
domDict = {"CI":"Cast iron", "DI": "Ductile iron", "PVC": "PVC",
"ACP": "Asbestos concrete", "COP": "Copper"}
# Process: Add valid material types to the domain
# use a for loop to cycle through all the domain codes in the dictionary
for code in domDict:
arcpy.AddCodedValueToDomain_management(gdb, domName, code, domDict[code])
# Process: Constrain the material value of distribution mains
arcpy.AssignDomainToField_management(inFeatures, inField, domName)