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resource

The Resource class wraps a Graph and a resource reference (i.e. a URIRef or BNode) to support a resource-oriented way of working with a graph.

It contains methods directly corresponding to those methods of the Graph interface that relate to reading and writing data. The difference is that a Resource also binds a resource identifier, making it possible to work without tracking both the graph and a current subject. This makes for a “resource oriented” style, as compared to the triple orientation of the Graph API.

Resulting generators are also wrapped so that any resource reference values (URIRef and BNode) are in turn wrapped as Resources. (Note that this behaviour differs from the corresponding methods in Graph, where no such conversion takes place.)

Basic Usage Scenario

Start by importing things we need and define some namespaces:

>>> from rdflib import *
>>> FOAF = Namespace("http://xmlns.com/foaf/0.1/")
>>> CV = Namespace("http://purl.org/captsolo/resume-rdf/0.2/cv#")

Load some RDF data:

>>> graph = Graph().parse(format='n3', data='''
... @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
... @prefix xsd: <http://www.w3.org/2001/XMLSchema#>.
... @prefix foaf: <http://xmlns.com/foaf/0.1/> .
... @prefix cv: <http://purl.org/captsolo/resume-rdf/0.2/cv#> .
...
... @base <http://example.org/> .
...
... </person/some1#self> a foaf:Person;
...     rdfs:comment "Just a Python & RDF hacker."@en;
...     foaf:depiction </images/person/some1.jpg>;
...     foaf:homepage <http://example.net/>;
...     foaf:name "Some Body" .
...
... </images/person/some1.jpg> a foaf:Image;
...     rdfs:label "some 1"@en;
...     rdfs:comment "Just an image"@en;
...     foaf:thumbnail </images/person/some1-thumb.jpg> .
...
... </images/person/some1-thumb.jpg> a foaf:Image .
...
... [] a cv:CV;
...     cv:aboutPerson </person/some1#self>;
...     cv:hasWorkHistory [ cv:employedIn </#company>;
...             cv:startDate "2009-09-04"^^xsd:date ] .
... ''')

Create a Resource:

>>> person = Resource(
...     graph, URIRef("http://example.org/person/some1#self"))

Retrieve some basic facts:

>>> person.identifier
rdflib.term.URIRef('http://example.org/person/some1#self')

>>> person.value(FOAF.name)
rdflib.term.Literal('Some Body')

>>> person.value(RDFS.comment)
rdflib.term.Literal('Just a Python & RDF hacker.', lang='en')

Resources can be sliced (like graphs, but the subject is fixed):

>>> for name in person[FOAF.name]:
...     print(name)
Some Body
>>> person[FOAF.name : Literal("Some Body")]
True

Resources as unicode are represented by their identifiers as unicode:

>>> %(unicode)s(person)  #doctest: +SKIP
'Resource(http://example.org/person/some1#self'

Resource references are also Resources, so you can easily get e.g. a qname for the type of a resource, like:

>>> person.value(RDF.type).qname()
'foaf:Person'

Or for the predicates of a resource:

>>> sorted(
...     p.qname() for p in person.predicates()
... )  #doctest: +NORMALIZE_WHITESPACE +SKIP
['foaf:depiction', 'foaf:homepage',
 'foaf:name', 'rdf:type', 'rdfs:comment']

Follow relations and get more data from their Resources as well:

>>> for pic in person.objects(FOAF.depiction):
...     print(pic.identifier)
...     print(pic.value(RDF.type).qname())
...     print(pic.value(FOAF.thumbnail).identifier)
http://example.org/images/person/some1.jpg
foaf:Image
http://example.org/images/person/some1-thumb.jpg

>>> for cv in person.subjects(CV.aboutPerson):
...     work = list(cv.objects(CV.hasWorkHistory))[0]
...     print(work.value(CV.employedIn).identifier)
...     print(work.value(CV.startDate))
http://example.org/#company
2009-09-04

It’s just as easy to work with the predicates of a resource:

>>> for s, p in person.subject_predicates():
...     print(s.value(RDF.type).qname())
...     print(p.qname())
...     for s, o in p.subject_objects():
...         print(s.value(RDF.type).qname())
...         print(o.value(RDF.type).qname())
cv:CV
cv:aboutPerson
cv:CV
foaf:Person

This is useful for e.g. inspection:

>>> thumb_ref = URIRef("http://example.org/images/person/some1-thumb.jpg")
>>> thumb = Resource(graph, thumb_ref)
>>> for p, o in thumb.predicate_objects():
...     print(p.qname())
...     print(o.qname())
rdf:type
foaf:Image

Schema Example

With this artificial schema data:

>>> graph = Graph().parse(format='n3', data='''
... @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
... @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
... @prefix owl: <http://www.w3.org/2002/07/owl#> .
... @prefix v: <http://example.org/def/v#> .
...
... v:Artifact a owl:Class .
...
... v:Document a owl:Class;
...     rdfs:subClassOf v:Artifact .
...
... v:Paper a owl:Class;
...     rdfs:subClassOf v:Document .
...
... v:Choice owl:oneOf (v:One v:Other) .
...
... v:Stuff a rdf:Seq; rdf:_1 v:One; rdf:_2 v:Other .
...
... ''')

From this class:

>>> artifact = Resource(graph, URIRef("http://example.org/def/v#Artifact"))

we can get at subclasses:

>>> subclasses = list(artifact.transitive_subjects(RDFS.subClassOf))
>>> [c.qname() for c in subclasses]
['v:Artifact', 'v:Document', 'v:Paper']

and superclasses from the last subclass:

>>> [c.qname() for c in subclasses[-1].transitive_objects(RDFS.subClassOf)]
['v:Paper', 'v:Document', 'v:Artifact']

Get items from the Choice:

>>> choice = Resource(graph, URIRef("http://example.org/def/v#Choice"))
>>> [it.qname() for it in choice.value(OWL.oneOf).items()]
['v:One', 'v:Other']

On add, other resources are auto-unboxed:

>>> paper = Resource(graph, URIRef("http://example.org/def/v#Paper"))
>>> paper.add(RDFS.subClassOf, artifact)
>>> artifact in paper.objects(RDFS.subClassOf) # checks Resource instance
True
>>> (paper._identifier, RDFS.subClassOf, artifact._identifier) in graph
True

Technical Details

Comparison is based on graph and identifier:

>>> g1 = Graph()
>>> t1 = Resource(g1, URIRef("http://example.org/thing"))
>>> t2 = Resource(g1, URIRef("http://example.org/thing"))
>>> t3 = Resource(g1, URIRef("http://example.org/other"))
>>> t4 = Resource(Graph(), URIRef("http://example.org/other"))

>>> t1 is t2
False

>>> t1 == t2
True
>>> t1 != t2
False

>>> t1 == t3
False
>>> t1 != t3
True

>>> t3 != t4
True

>>> t3 < t1 and t1 > t3
True
>>> t1 >= t1 and t1 >= t3
True
>>> t1 <= t1 and t3 <= t1
True

>>> t1 < t1 or t1 < t3 or t3 > t1 or t3 > t3
False

Hash is computed from graph and identifier:

>>> g1 = Graph()
>>> t1 = Resource(g1, URIRef("http://example.org/thing"))

>>> hash(t1) == hash(Resource(g1, URIRef("http://example.org/thing")))
True

>>> hash(t1) == hash(Resource(Graph(), t1.identifier))
False
>>> hash(t1) == hash(Resource(Graph(), URIRef("http://example.org/thing")))
False

The Resource class is suitable as a base class for mapper toolkits. For example, consider this utility for accessing RDF properties via qname-like attributes:

>>> class Item(Resource):
...
...     def __getattr__(self, p):
...         return list(self.objects(self._to_ref(*p.split('_', 1))))
...
...     def _to_ref(self, pfx, name):
...         return URIRef(self._graph.store.namespace(pfx) + name)

It works as follows:

>>> graph = Graph().parse(format='n3', data='''
... @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
... @prefix foaf: <http://xmlns.com/foaf/0.1/> .
...
... @base <http://example.org/> .
... </person/some1#self>
...     foaf:name "Some Body";
...     foaf:depiction </images/person/some1.jpg> .
... </images/person/some1.jpg> rdfs:comment "Just an image"@en .
... ''')

>>> person = Item(graph, URIRef("http://example.org/person/some1#self"))

>>> print(person.foaf_name[0])
Some Body

The mechanism for wrapping references as resources cooperates with subclasses. Therefore, accessing referenced resources automatically creates new Item objects:

>>> isinstance(person.foaf_depiction[0], Item)
True

>>> print(person.foaf_depiction[0].rdfs_comment[0])
Just an image

Classes:

  • Resource –

    A Resource is a wrapper for a graph and a resource identifier.

__all__ module-attribute 

__all__ = ['Resource']

Resource 

Resource(graph, subject)

A Resource is a wrapper for a graph and a resource identifier.

Methods:

Attributes:

Source code in rdflib/resource.py 
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def __init__(self, graph, subject):
    self._graph = graph
    self._identifier = subject

graph property 

graph

identifier property 

identifier

__eq__ 

__eq__(other)
Source code in rdflib/resource.py 
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def __eq__(self, other):
    return (
        isinstance(other, Resource)
        and self._graph == other._graph
        and self._identifier == other._identifier
    )

__ge__ 

__ge__(other)
Source code in rdflib/resource.py 
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def __ge__(self, other):
    return not self < other

__getitem__ 

__getitem__(item)
Source code in rdflib/resource.py 
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def __getitem__(self, item):
    if isinstance(item, slice):
        if item.step:
            raise TypeError(
                "Resources fix the subject for slicing, and can only be sliced by predicate/object. "
            )
        p, o = item.start, item.stop
        if isinstance(p, Resource):
            p = p._identifier
        if isinstance(o, Resource):
            o = o._identifier
        if p is None and o is None:
            return self.predicate_objects()
        elif p is None:
            return self.predicates(o)
        elif o is None:
            return self.objects(p)
        else:
            return (self.identifier, p, o) in self._graph
    elif isinstance(item, (Node, Path)):
        return self.objects(item)
    else:
        raise TypeError(
            "You can only index a resource by a single rdflib term, a slice of rdflib terms, not %s (%s)"
            % (item, type(item))
        )

__gt__ 

__gt__(other)
Source code in rdflib/resource.py 
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def __gt__(self, other):
    return not (self < other or self == other)

__hash__ 

__hash__()
Source code in rdflib/resource.py 
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def __hash__(self):
    return hash(Resource) ^ hash(self._graph) ^ hash(self._identifier)

__iter__ 

__iter__()
Source code in rdflib/resource.py 
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def __iter__(self):
    return self._resource_triples(
        self._graph.triples((self.identifier, None, None))
    )

__le__ 

__le__(other)
Source code in rdflib/resource.py 
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def __le__(self, other):
    return self < other or self == other

__lt__ 

__lt__(other)
Source code in rdflib/resource.py 
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def __lt__(self, other):
    if isinstance(other, Resource):
        return self._identifier < other._identifier
    else:
        return False

__ne__ 

__ne__(other)
Source code in rdflib/resource.py 
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def __ne__(self, other):
    return not self == other

__repr__ 

__repr__()
Source code in rdflib/resource.py 
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def __repr__(self):
    return "Resource(%s,%s)" % (self._graph, self._identifier)

__setitem__ 

__setitem__(item, value)
Source code in rdflib/resource.py 
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def __setitem__(self, item, value):
    self.set(item, value)

__str__ 

__str__()
Source code in rdflib/resource.py 
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def __str__(self):
    return "Resource(%s)" % self._identifier

__unicode__ 

__unicode__()
Source code in rdflib/resource.py 
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def __unicode__(self):
    return str(self._identifier)

add 

add(p, o)
Source code in rdflib/resource.py 
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def add(self, p, o):
    if isinstance(o, Resource):
        o = o._identifier

    self._graph.add((self._identifier, p, o))

items 

items()
Source code in rdflib/resource.py 
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def items(self):
    return self._resources(self._graph.items(self._identifier))

objects 

objects(predicate=None)
Source code in rdflib/resource.py 
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def objects(self, predicate=None):
    return self._resources(self._graph.objects(self._identifier, predicate))

predicate_objects 

predicate_objects()
Source code in rdflib/resource.py 
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def predicate_objects(self):
    return self._resource_pairs(self._graph.predicate_objects(self._identifier))

predicates 

predicates(o=None)
Source code in rdflib/resource.py 
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def predicates(self, o=None):
    if isinstance(o, Resource):
        o = o._identifier

    return self._resources(self._graph.predicates(self._identifier, o))

qname 

qname()
Source code in rdflib/resource.py 
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def qname(self):
    return self._graph.qname(self._identifier)

remove 

remove(p, o=None)
Source code in rdflib/resource.py 
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def remove(self, p, o=None):
    if isinstance(o, Resource):
        o = o._identifier

    self._graph.remove((self._identifier, p, o))

set 

set(p, o)
Source code in rdflib/resource.py 
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def set(self, p, o):
    if isinstance(o, Resource):
        o = o._identifier

    self._graph.set((self._identifier, p, o))

subject_objects 

subject_objects()
Source code in rdflib/resource.py 
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def subject_objects(self):
    return self._resource_pairs(self._graph.subject_objects(self._identifier))

subject_predicates 

subject_predicates()
Source code in rdflib/resource.py 
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def subject_predicates(self):
    return self._resource_pairs(self._graph.subject_predicates(self._identifier))

subjects 

subjects(predicate=None)
Source code in rdflib/resource.py 
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def subjects(self, predicate=None):  # rev
    return self._resources(self._graph.subjects(predicate, self._identifier))

transitive_objects 

transitive_objects(predicate, remember=None)
Source code in rdflib/resource.py 
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def transitive_objects(self, predicate, remember=None):
    return self._resources(
        self._graph.transitive_objects(self._identifier, predicate, remember)
    )

transitive_subjects 

transitive_subjects(predicate, remember=None)
Source code in rdflib/resource.py 
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def transitive_subjects(self, predicate, remember=None):
    return self._resources(
        self._graph.transitive_subjects(predicate, self._identifier, remember)
    )

value 

value(p=value, o=None, default=None, any=True)
Source code in rdflib/resource.py 
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def value(self, p=RDF.value, o=None, default=None, any=True):
    if isinstance(o, Resource):
        o = o._identifier

    return self._cast(self._graph.value(self._identifier, p, o, default, any))