First steps with RDFAlchemy and SPARQL to access DBPedia

rdfalchemy_test_dbpedia.py

from rdfalchemy.sparql import SPARQLGraph
from rdflib import Namespace

query = """
PREFIX db: <http://dbpedia.org/resource/>
PREFIX dbonto: <http://dbpedia.org/ontology/>

SELECT DISTINCT ?who
FROM <http://dbpedia.org>
WHERE {
    ?who dbonto:genre db:Metal .
}
"""

endpoint = "http://dbpedia.org/sparql"
graph = SPARQLGraph(endpoint)

# Option 1: Running raw query
metal_guys1 = list(graph.query(query, resultMethod='xml'))
print u"Number of things with genre Metal", len(metal_guys1)
# output: 43


# Option 2: Calling using namespaces and subjects
DB = Namespace('http://dbpedia.org/resource/')
DBONTO = Namespace("http://dbpedia.org/ontology/")

metal_guys2 = list(graph.subjects(predicate=DB.genre, object=DBONTO.Metal))
print u"Number of things with genre Metal", len(metal_guys2)
# output: 0

assert metal_guys1 == metal_guys2
# :( AssertionError

This code has a problem. Line 28 should be:

metal_guys2 = list(graph.subjects(predicate=DBONTO.genre, object=DB.Metal))

Also, it is needed to sort the lists before the assert, on line 32.