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from rdflib.namespace import RDF, NamespaceManager
class RDFWalker:
"""
Simple RDF graph walker
"""
def __init__ (self, g, s, n, path=[]):
"""
:param g: Graph
:param s: Namespace
:param n: Start node
"""
self.g = g
self.n = n
self.s = s
self._path = path
def __getattr__ (self, k):
"""
If k is underscore _, walk up tree one level, otherwise search for
direct descendents and get first one.
"""
if k == '_':
return RDFWalker (self.g, self.s, self._path[0], self._path[1:])
yieldall = False
if k.endswith ('_'):
yieldall = True
k = k[:-1]
if k == 'a':
attr = RDF.type
else:
attr = getattr (self.s, k)
ret = [RDFWalker (self.g, self.s, n, [self.n] + self._path) for n in self.g.objects (self.n, attr)]
if yieldall:
return ret
elif not ret:
return None
else:
return ret[0]
def __eq__ (self, b):
return self.n == b.n
def __lt__ (self, b):
return str (self) < str (b)
def __str__ (self):
return str (self.n)
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