class RdfParser(object):
"""A basic wrapper for RdfLib's RDF parser.
This class aims to accomplish easier parsing, extraction of Models,
etc."""
def __init__(self, rdf, format='guess'):
"""Init the parser with the graph string."""
self.graph = Graph()
if format == 'guess':
format = self.__guess_format(rdf)
print 'RdfParser guesses format to be: %s' % format
try:
self.graph.load(StringIO(rdf), format=format)
except:
print "Failed to parse RDF:"
print rdf[0:100]
def extract(self, datatype):
"""Extract all of the data of a given datatype."""
data = []
ns = RdfSerializer.NAMESPACES['sylph'] # TODO: Awkward.
for sub in self.graph.subjects(RDF.type, ns[datatype]):
idx = str(sub)
item = {'uri': idx}
for pred, obj in self.graph.predicate_objects(sub):
if pred == RDF.type:
continue
if obj == ns['None']:
obj = None
elif type(obj) == URIRef:
obj = unicode(obj)
elif type(obj) == Literal:
obj = obj.toPython()
if type(obj) == Literal: # Don't be silly, RdfLib!
obj = unicode(obj)
predstr = str(pred).rpartition('#')[2].rpartition('/')[2]
item[predstr] = obj
data.append(item)
return data
@staticmethod
def __guess_format(st):
"""Guess the format of the input string."""
# TODO: At present, it can only guess between XML and n3, even
# then this is a vague heuristic.
if st.startswith('<'):
return 'xml'
return 'n3'
