Source code for rdflib.plugins.serializers.nt
"""
N-Triples RDF graph serializer for RDFLib.
See <http://www.w3.org/TR/rdf-testcases/#ntriples> for details about the
format.
"""
from rdflib.term import Literal
from rdflib.serializer import Serializer
from rdflib.py3compat import b
import warnings
__all__ = ['NTSerializer']
[docs]class NTSerializer(Serializer):
"""
Serializes RDF graphs to NTriples format.
"""
[docs] def serialize(self, stream, base=None, encoding=None, **args):
if base is not None:
warnings.warn("NTSerializer does not support base.")
if encoding is not None:
warnings.warn("NTSerializer does not use custom encoding.")
encoding = self.encoding
for triple in self.store:
stream.write(_nt_row(triple).encode(encoding, "replace"))
stream.write(b("\n"))
def _nt_row(triple):
if isinstance(triple[2], Literal):
return u"%s %s %s .\n" % (
triple[0].n3(),
triple[1].n3(),
_xmlcharref_encode(_quoteLiteral(triple[2])))
else:
return u"%s %s %s .\n" % (triple[0].n3(),
triple[1].n3(),
_xmlcharref_encode(triple[2].n3()))
def _quoteLiteral(l):
'''
a simpler version of term.Literal.n3()
'''
encoded = _quote_encode(l)
if l.language:
if l.datatype:
raise Exception("Literal has datatype AND language!")
return '%s@%s' % (encoded, l.language)
elif l.datatype:
return '%s^^<%s>' % (encoded, l.datatype)
else:
return '%s' % encoded
def _quote_encode(l):
return '"%s"' % l.replace('\\', '\\\\')\
.replace('\n', '\\n')\
.replace('"', '\\"')\
.replace('\r', '\\r')
# from <http://code.activestate.com/recipes/303668/>
def _xmlcharref_encode(unicode_data, encoding="ascii"):
"""Emulate Python 2.3's 'xmlcharrefreplace' encoding error handler."""
res = ""
# Step through the unicode_data string one character at a time in
# order to catch unencodable characters:
for char in unicode_data:
try:
char.encode(encoding, 'strict')
except UnicodeError:
if ord(char) <= 0xFFFF:
res += '\\u%04X' % ord(char)
else:
res += '\\U%08X' % ord(char)
else:
res += char
return res