We recently released the xOCLCNUM service in
http://xisbn.worldcat.org/xisbnadmin/xoclcnum/index.htm
In the early design of xISBN service, we didn't think through all requirement for future services, so it's bit awkward that we actually use a different XML schema/namespace for xOCLCNUM service, such as:
<rsp xmlns="http://worldcat.org/xid/oclcnum/" stat="ok">
<oclcnum isbn="9780596002817" lccn="2004273129">55847258</oclcnum>
</rsp>
However, if you prefer to use any other dissemination format, such as text or json distribution, we actually kept a consistent schema:
http://xisbn.worldcat.org/webservices/xid/isbn/0596002815
?method=getMetadata&format=python&fl=isbn,oclcnum
http://xisbn.worldcat.org/webservices/xid/oclcnum/177669176
?method=getMetadata&format=python&fl=isbn,oclcnum
So any code written for xISBN should be applicable to xOCLCNUM as well if you are not using XML dissemination, otherwise you may need a little (I hope) adjustments.