How do I detect relationship classes in a file GDB?

Question

I would like to be able to detect relationship classes in a file GDB. Because users of my script might have only an ArcView level license, they would not be able to manipulate the schema of a feature class (specifically to add a field) that is in a workspace that has relationship classes. How do I detect the presence of relationship classes, so that I can document them, avoid them programatically, and allow the script to continue?

Answer 1

The relationshipClassNames property is supposed to do this but it does not seem to work for me (tested in a file geodatabase, created relationship class between two feature classes, checked the property, the list returned is empty for both). Maybe it will work for you.

Answer 2

This python code lists all relationship classes within a Geodatabase and put them in a unique list (relClasses):

inGDB = r"D:\mygeodatabase.gdb"
env.workspace = inGDB
#################Getting all Tables and Feature Classes###########
fcs = []
#root of workspace
for item in arcpy.ListFeatureClasses("*"):    fcs.append(item)
for item in arcpy.ListTables("*"):    fcs.append(item)

fds = arcpy.ListDatasets("*","Feature")
for fd in fds:
    env.workspace = inGDB +'\\'+fd
    for fc in arcpy.ListFeatureClasses("*"):
        fcs.append(fd+'/'+fc)
    for tb in arcpy.ListTables("*"):
        fcs.append(fd+'/'+tb)
        
env.workspace = inGDB
relClasses = set()
for i,fc in enumerate(fcs): 
    desc = arcpy.Describe(fc)
    for j,rel in enumerate(desc.relationshipClassNames):
        relDesc = arcpy.Describe(rel)
        if relDesc.isAttachmentRelationship:
            continue
        relClasses.add(rel)

print relClasses

Answer 3

I struggled with this until realizing arcpy sees relationship classes through the tables with which they are associated. Here's a little piece of code to check for relationship class names greater than length 30:

arcpy.env.workspace = 'C:/workspace'

# Local variables
tables = arcpy.ListTables()

# Iterate through tables in file geodatabase (workspace)
for t in tables:
    # Get relationship class(es) associated with table
    desc = arcpy.Describe(t)
    rcs = desc.relationshipClassNames
# Iterate through any relationship classes associated with current table in loop
    for r in rcs:
        if len(r) > 30:
            print 'Relationship class ' + r + ' has ' + str(len(r)) + ' characters.'

Answer 4

I am at 10.5.1 and it looks like the relationshipClassNames is giving me the list of relationship class names like it supposed to

layer = "C:\\Geodatabases\\somegeodatabase.gdb\\my_layer"
desc = arcpy.Describe(layer)
print desc.relationshipClassNames