Merge pull request #503 from joernhees/fix_from_n3

fix util.from_n3() parsing Literals with datatypes and Namespace support, fixes #502

Author: joernhees

rdflib/util.py

@@ -46,6 +46,8 @@
 from rdflib.exceptions import SubjectTypeError
 from rdflib.graph import Graph
 from rdflib.graph import QuotedGraph
+from rdflib.namespace import Namespace
+from rdflib.namespace import NamespaceManager
 from rdflib.term import BNode
 from rdflib.term import Literal
 from rdflib.term import URIRef
@@ -122,7 +124,7 @@ def to_term(s, default=None):
         raise Exception(msg)
 
 
-def from_n3(s, default=None, backend=None):
+def from_n3(s, default=None, backend=None, nsm=None):
     r'''
     Creates the Identifier corresponding to the given n3 string.
 
@@ -135,10 +137,20 @@ def from_n3(s, default=None, backend=None):
         True
         >>> from_n3('42') == Literal(42)
         True
+        >>> from_n3(Literal(42).n3()) == Literal(42)
+        True
+        >>> from_n3('"42"^^xsd:integer') == Literal(42)
+        True
+        >>> from rdflib import RDFS
+        >>> from_n3('rdfs:label') == RDFS['label']
+        True
+        >>> nsm = NamespaceManager(Graph())
+        >>> nsm.bind('dbpedia', 'http://dbpedia.org/resource/')
+        >>> berlin = URIRef('http://dbpedia.org/resource/Berlin')
+        >>> from_n3('dbpedia:Berlin', nsm=nsm) == berlin
+        True
 
     '''
-    # TODO: should be able to handle prefixes given as opt. argument maybe:
-    # from_n3('rdfs:label')
     if not s:
         return default
     if s.startswith('<'):
@@ -160,7 +172,7 @@ def from_n3(s, default=None, backend=None):
             # datatype has to come after lang-tag so ignore everything before
             # see: http://www.w3.org/TR/2011/WD-turtle-20110809/
             # #prod-turtle2-RDFLiteral
-            datatype = rest[dtoffset + 2:]
+            datatype = from_n3(rest[dtoffset + 2:], default, backend, nsm)
         else:
             if rest.startswith("@"):
                 language = rest[1:]  # strip leading at sign
@@ -180,11 +192,17 @@ def from_n3(s, default=None, backend=None):
     elif s.startswith('['):
         identifier = from_n3(s[1:-1])
         return Graph(backend, identifier)
+    elif s.startswith("_:"):
+        return BNode(s[2:])
+    elif ':' in s:
+        if nsm is None:
+            # instantiate default NamespaceManager and rely on its defaults
+            nsm = NamespaceManager(Graph())
+        prefix, last_part = s.split(':', 1)
+        ns = dict(nsm.namespaces())[prefix]
+        return Namespace(ns)[last_part]
     else:
-        if s.startswith("_:"):
-            return BNode(s[2:])
-        else:
-            return BNode(s)
+        return BNode(s)
 
 
 def check_context(c):

test/test_util.py

@@ -7,6 +7,7 @@
 from rdflib.term import Literal
 from rdflib.term import URIRef
 from rdflib import util
+from rdflib import XSD
 from rdflib.exceptions import SubjectTypeError
 from rdflib.exceptions import PredicateTypeError
 from rdflib.exceptions import ObjectTypeError
@@ -193,13 +194,13 @@ def test_util_from_n3_expectliteralandlangdtype(self):
         res = util.from_n3(s, default=None, backend=None)
         self.assert_(isinstance(res, Literal))
         self.assertEqual(res, Literal('michel',
-                                      datatype=URIRef('xsd:fr')))
-    
+                                      datatype=XSD['fr']))
+
     def test_util_from_n3_expectliteralanddtype(self):
         s = '"true"^^xsd:boolean'
         res = util.from_n3(s, default=None, backend=None)
-        self.assertTrue(res.eq(Literal('true', datatype='xsd:boolean')))
-    
+        self.assertTrue(res.eq(Literal('true', datatype=XSD['boolean'])))
+
     def test_util_from_n3_expectliteralwithdatatypefromint(self):
         s = '42'
         res = util.from_n3(s)
@@ -263,12 +264,12 @@ def parse_n3(term_n3):
 
 
     def test_util_from_n3_expectquotedgraph(self):
-        s = '{http://example.com/schema}'
+        s = '{<http://example.com/schema>}'
         res = util.from_n3(s, default=None, backend="IOMemory")
         self.assert_(isinstance(res, QuotedGraph))
 
     def test_util_from_n3_expectgraph(self):
-        s = '[http://example.com/schema]'
+        s = '[<http://example.com/schema>]'
         res = util.from_n3(s, default=None, backend="IOMemory")
         self.assert_(isinstance(res, Graph))