RDFLib provides mechanisms for managing Namespaces. In particular, there is a [http://svn.rdflib.net/trunk/rdflib/Namespace.py Namespace] class which takes (as its only argument) the Base URI of the namespace. Fully qualified URIs in the namespace can be constructed by attribute / dictionary access on Namespace instances:
>>> from rdflib.namespace import Namespace
>>> fuxi = Namespace('http://metacognition.info/ontologies/FuXi.n3#')
>>> fuxi.ruleBase
u'http://metacognition.info/ontologies/FuXi.n3#ruleBase'
>>> fuxi['ruleBase']
u'http://metacognition.info/ontologies/FuXi.n3#ruleBase'