arcpy.Exists doesn't handle domains. The ESRI help indicates what it does handle.
So you'll need to get a list of existing domains, and then check your potential new name against the list. What version of ArcGIS are you using? 10.1 introduces a new
If you're on ArcGIS 10.0, then you don't have this
ListDomains. In that case I think you should go with the answer to How to check if domain already exists?, which describes how to use the workspace
Describe function to check for existence.
If you're on ArcGIS 10.1, then you can try out the new
ListDomains function (data access module) to get a list of existing domain names for a geodatabase, and then compare your potential new name to the list of existing names.
Something like this:
myNewDomains = ['new one', 'new two']
existingDomains = arcpy.da.ListDomains("C:/xyz/xyz.gdb")
for myNewDomain in myNewDomains:
# check if myNewDomain already exists
found = False
for domain in existingDomains:
if domain.name == myNewDomain:
found = True
# if myNewDomain doesn't already exist, then create it
if found = False:
# drop in your domain-creation code
print "Domain already exists:", myNewDomain