Bill Kearney

Parsing RDF with python

I posted my article Some RDF examples and then I asked the RDF crowd in #rdfig to chime in with some comments. They pointed out a syntax error or two. But even better, Dan Connolly took the example and whipped up a quick snippet of code that reads it. He posted it into my comment section but I've cleaned up the formatting a bit and posted it again here. Firstly, make sure you've got python and the rdflib installed and running. Once that's done, put this snippet into a file named foafwk.py:

# cribbed from
#  http://rdflib.net/stable/example.py

from rdflib.TripleStore import TripleStore
from rdflib.constants import TYPE
from rdflib.Namespace import Namespace
from rdflib.Literal import Literal

FOAF = Namespace("http://xmlns.com/foaf/0.1/")
EX = Namespace("http://example.org/foovocab#")

def main():
    s = TripleStore()
    s.load(",ex2.rdf")

    # find a guy named bob...
    for who in s.subjects(FOAF["name"], Literal("Bob")):
        bob = who
    
    # who is secretlyStalking bob?
    for who in s.subjects(EX["secretlyStalking"], bob):
        for n in s.objects(who, FOAF["name"]):
            print n, "is secretlyStalking Bob!"

if __name__ == '__main__':
    main()

Then go take third example RDF and paste it into a file named ex2.rdf

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:eg="http://example.org/foovocab#"
  xmlns:foaf="http://xmlns.com/foaf/0.1/">
	<foaf:Person rdf:nodeID="alice">
	    <foaf:name>Alice</foaf:name>
	    <foaf:knows rdf:nodeID="bob"/>
	    <foaf:knows rdf:nodeID="ted"/>
	    <eg:acquaintance rdf:nodeID="bob"/>
	    <eg:acquaintance rdf:nodeID="ted"/>
	    <eg:archNemesis rdf:nodeID="bob"/>
	    <eg:archNemesis rdf:nodeID="ted"/>
	</foaf:Person>
	<foaf:Person rdf:nodeID="bob">
	    <foaf:knows rdf:nodeID="alice"/>
	    <foaf:knows rdf:nodeID="ted"/>
	    <foaf:name>Bob</foaf:name>
	    <eg:secretlyStalking rdf:nodeID="alice"/>
	    <eg:acquaintance rdf:nodeID="alice"/>
	    <eg:archNemesis rdf:nodeID="ted"/>
	</foaf:Person>
	<foaf:Person rdf:nodeID="carol">
	    <foaf:name>Carol</foaf:name>
	    <foaf:knows rdf:nodeID="alice"/>
	    <foaf:knows rdf:nodeID="ted"/>
	    <eg:secretlyStalking rdf:nodeID="bob"/>
	    <eg:acquaintance rdf:nodeID="alice"/>
	    <eg:acquaintance rdf:nodeID="ted"/>
	</foaf:Person>
	<foaf:Person rdf:nodeID="ted">
	    <foaf:name>Ted</foaf:name>
	    <eg:acquaintance rdf:nodeID="carol"/>
	    <eg:acquaintance rdf:nodeID="alice"/>
	    <eg:archNemesis rdf:nodeID="bob"/>
	</foaf:Person>
</rdf:RDF>

Now execute the program:

$ python foafwk.py ,ex2.rdf
Carol is secretlyStalking Bob!

You can fiddle around with the ex2.rdf file and the python example to learn what more can be done. Post a comment