Getting started with RDFLib

Installation

RDFLib is open source and is maintained in a GitHub repository. RDFLib releases, current and previous, are listed on PyPi

The best way to install RDFLib is to use pip (sudo as required):

$ pip install rdflib

If you want the latest code to run, clone the main branch of the GitHub repo and use that or you can pip install directly from GitHub:

$ pip install git+https://github.com/RDFLib/rdflib.git@main#egg=rdflib

Support

Usage support is available via questions tagged with [rdflib] on StackOverflow and development support, notifications and detailed discussion through the rdflib-dev group (mailing list):

http://groups.google.com/group/rdflib-dev

If you notice an bug or want to request an enhancement, please do so via our Issue Tracker in Github:

http://github.com/RDFLib/rdflib/issues

How it all works

The package uses various Python idioms that offer an appropriate way to introduce RDF to a Python programmer who hasn’t worked with RDF before.

The primary interface that RDFLib exposes for working with RDF is a Graph.

RDFLib graphs are un-sorted containers; they have ordinary Python set operations (e.g. add() to add a triple) plus methods that search triples and return them in arbitrary order.

RDFLib graphs also redefine certain built-in Python methods in order to behave in a predictable way. They do this by emulating container types and are best thought of as a set of 3-item tuples (“triples”, in RDF-speak):

[
    (subject0, predicate0, object0),
    (subject1, predicate1, object1),
    ...
    (subjectN, predicateN, objectN)
 ]

A tiny example

from rdflib import Graph

# Create a Graph
g = Graph()

# Parse in an RDF file hosted on the Internet
g.parse("http://www.w3.org/People/Berners-Lee/card")

# Loop through each triple in the graph (subj, pred, obj)
for subj, pred, obj in g:
    # Check if there is at least one triple in the Graph
    if (subj, pred, obj) not in g:
       raise Exception("It better be!")

# Print the number of "triples" in the Graph
print(f"Graph g has {len(g)} statements.")
# Prints: Graph g has 86 statements.

# Print out the entire Graph in the RDF Turtle format
print(g.serialize(format="turtle"))

Here a Graph is created and then an RDF file online, Tim Berners-Lee’s social network details, is parsed into that graph. The print() statement uses the len() function to count the number of triples in the graph.

A more extensive example

from rdflib import Graph, Literal, RDF, URIRef
# rdflib knows about quite a few popular namespaces, like W3C ontologies, schema.org etc.
from rdflib.namespace import FOAF , XSD

# Create a Graph
g = Graph()

# Create an RDF URI node to use as the subject for multiple triples
donna = URIRef("http://example.org/donna")

# Add triples using store's add() method.
g.add((donna, RDF.type, FOAF.Person))
g.add((donna, FOAF.nick, Literal("donna", lang="en")))
g.add((donna, FOAF.name, Literal("Donna Fales")))
g.add((donna, FOAF.mbox, URIRef("mailto:donna@example.org")))

# Add another person
ed = URIRef("http://example.org/edward")

# Add triples using store's add() method.
g.add((ed, RDF.type, FOAF.Person))
g.add((ed, FOAF.nick, Literal("ed", datatype=XSD.string)))
g.add((ed, FOAF.name, Literal("Edward Scissorhands")))
g.add((ed, FOAF.mbox, Literal("e.scissorhands@example.org", datatype=XSD.anyURI)))

# Iterate over triples in store and print them out.
print("--- printing raw triples ---")
for s, p, o in g:
    print((s, p, o))

# For each foaf:Person in the store, print out their mbox property's value.
print("--- printing mboxes ---")
for person in g.subjects(RDF.type, FOAF.Person):
    for mbox in g.objects(person, FOAF.mbox):
        print(mbox)

# Bind the FOAF namespace to a prefix for more readable output
g.bind("foaf", FOAF)

# print all the data in the Notation3 format
print("--- printing mboxes ---")
print(g.serialize(format='n3'))

A SPARQL query example

from rdflib import Graph

# Create a Graph, pare in Internet data
g = Graph().parse("http://www.w3.org/People/Berners-Lee/card")

# Query the data in g using SPARQL
# This query returns the 'name' of all ``foaf:Person`` instances
q = """
    PREFIX foaf: <http://xmlns.com/foaf/0.1/>

    SELECT ?name
    WHERE {
        ?p rdf:type foaf:Person .

        ?p foaf:name ?name .
    }
"""

# Apply the query to the graph and iterate through results
for r in g.query(q):
    print(r["name"])

# prints: Timothy Berners-Lee

More examples

There are many more examples in the examples folder in the source distribution.