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"""
SPARQL Query using [`Graph.query`][rdflib.graph.Graph.query]
The method returns a [`Result`][rdflib.query.Result], iterating over
this yields [`ResultRow`][rdflib.query.ResultRow] objects
The variable bindings can be accessed as attributes of the row objects
For variable names that are not valid python identifiers, dict access
(i.e. with `row[var] / __getitem__`) is also possible.
[`Result.vars`][rdflib.query.Result.vars] contains the variables
"""
import logging
import sys
from pathlib import Path
import rdflib
EXAMPLES_DIR = Path(__file__).parent
if __name__ == "__main__":
logging.basicConfig(level=logging.DEBUG, stream=sys.stderr)
g = rdflib.Graph()
g.parse(f"{EXAMPLES_DIR / 'foaf.n3'}", format="n3")
# The QueryProcessor knows the FOAF prefix from the graph
# which in turn knows it from reading the N3 RDF file
for row in g.query("SELECT ?s WHERE { [] foaf:knows ?s .}"):
# For select queries, the Result object is an iterable of ResultRow
# objects.
assert isinstance(row, rdflib.query.ResultRow)
print(row.s)
# or row["s"]
# or row[rdflib.Variable("s")]
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