def fetch_rdf_graph(subject, dont_follow=None):
"""Fetch all triples related to a subject and transform them to a graph.
First this function fetches all triples with the given subject. Then it
calls itself recursively for all such triples that have an URI as their
object. The end result is a clean graph of all these triples similar to
the output of make_graph().
Arguments:
subject -- The subject of triples to fetch.
dont_follow -- A list of predicates which are not followed recursively.
This is useful if the RDF graph contains recursive references that
cause infinite recursion in this function.
"""
if dont_follow is None:
dont_follow = []
with pool.get_connection() as sc:
triples = sc.query(Triple(subject, None, None))
graph = {}
if not triples:
return graph
for triple in triples:
# Skip triples that define RDF ontology
if triple.predicate.startswith(RDF_SYNTAX_NS_URI):
continue
subject = wrap_if_not_none(str, triple.subject)
predicate = wrap_if_not_none(str, triple.predicate)
object_ = wrap_if_not_none(str, triple.object)
# Strip namespace uri from predicate
if isinstance(triple.predicate, uri):
predicate = predicate.split('#')[-1]
# The last condition is there to prevent wandering into RDF
# ontology definitions
if isinstance(triple.object, uri) and \
str(triple.predicate) not in dont_follow and \
not object_.startswith(RDF_SCHEMA_URI):
value = fetch_rdf_graph(object_, dont_follow)
else:
value = object_
if subject not in graph:
graph[subject] = {}
if predicate not in graph[subject]:
graph[subject][predicate] = value
elif isinstance(graph[subject][predicate], list):
graph[subject][predicate].append(value)
else:
graph[subject][predicate] = [graph[subject][predicate], value]
return graph[subject]
def make_graph(triples):
"""Transforms a list of triples into a graph.
>>> from cloudsizzle.kp import Triple, uri, literal
>>> from pprint import pprint
>>> triples = [Triple('T-76.4115', 'rdf:type', 'Course'),
... Triple('T-76.4115', 'name', 'Software Development Project'),
... Triple('T-76.4115', 'extent', '5-8')]
>>> pprint(make_graph(triples))
{'T-76.4115': {'extent': '5-8',
'name': 'Software Development Project',
'rdf:type': 'Course'}}
When there are multiple triples with the same subject and predicate, the
objects of the triples are put in a list:
>>> triples = [
... Triple(
... 'http://cos.alpha.sizl.org/people/ID#dRq9He3yWr3QUKaaWPEYjL',
... 'rdf:type',
... 'http://cos.alpha.sizl.org/people#Person'),
... Triple(
... 'http://cos.alpha.sizl.org/people/ID#dRq9He3yWr3QUKaaWPEYjL',
... 'has_friend',
... 'http://cos.alpha.sizl.org/people/ID#azAC7-RdCr3OiIaaWPfx7J'),
... Triple(
... 'http://cos.alpha.sizl.org/people/ID#dRq9He3yWr3QUKaaWPEYjL',
... 'has_friend',
... 'http://cos.alpha.sizl.org/people/ID#azEe6yRdCr3OiIaaWPfx7J')]
>>> pprint(make_graph(triples))
{'http://cos.alpha.sizl.org/people/ID#dRq9He3yWr3QUKaaWPEYjL':
{'has_friend':
['http://cos.alpha.sizl.org/people/ID#azAC7-RdCr3OiIaaWPfx7J',
'http://cos.alpha.sizl.org/people/ID#azEe6yRdCr3OiIaaWPfx7J'],
'rdf:type': 'http://cos.alpha.sizl.org/people#Person'}}
"""
graph = {}
for triple in triples:
subject = wrap_if_not_none(str, triple.subject)
predicate = wrap_if_not_none(str, triple.predicate)
object_ = wrap_if_not_none(str, triple.object)
if subject not in graph:
graph[subject] = {}
if predicate not in graph[subject]:
graph[subject][predicate] = object_
elif isinstance(graph[subject][predicate], list):
graph[subject][predicate].append(object_)
else:
graph[subject][predicate] = [graph[subject][predicate], object_]
return graph