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"""
SPARQL 1.1 defines path operators for combining/repeating predicates
in triple-patterns.
We overload some Python operators on URIRefs to allow creating path
operators directly in Python.
| Operator | Path |
|-------------|----------------------------------------------------|
| `p1 / p2` | Path sequence |
| `p1 | p2` | Path alternative |
| `p1 * '*'` | Chain of 0 or more p's |
| `p1 * '+'` | Chain of 1 or more p's |
| `p1 * '?'` | 0 or 1 p |
| `~p1` | p1 inverted, i.e. `(s p1 o)` ⇔ `(o ~p1 s)` |
| `-p1` | NOT p1, i.e. any property but p1 |
These can then be used in property position for `s,p,o` triple queries
for any graph method.
See the docs for [`paths`][rdflib.paths] for the details.
This example shows how to get the name of friends (i.e values two steps away x knows y, y name z) with a single query.
"""
from pathlib import Path
from rdflib import Graph, URIRef
from rdflib.namespace import FOAF
EXAMPLES_DIR = Path(__file__).parent
if __name__ == "__main__":
g = Graph()
g.parse(f"{EXAMPLES_DIR / 'foaf.n3'}")
tim = URIRef("http://www.w3.org/People/Berners-Lee/card#i")
print("Timbl knows:")
for o in g.objects(tim, FOAF.knows / FOAF.name):
print(o)
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