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.. _gettingstarted:
===========================
Getting started with RDFLib
===========================
Installation
============
RDFLib is open source and is maintained in a
`GitHub <http://github.com/RDFLib/rdflib/>`_ repository. RDFLib releases, current and previous
are listed on `PyPi <pypi.python.org/pypi/rdflib/>`_
RDFLib may be easy_installed:
.. code-block :: bash
$ easy_install rdflib
Support is available through the rdflib-dev group::
http://groups.google.com/group/rdflib-dev
and on the IRC channel #redfoot on the freenode.net server
The primary interface that RDFLib exposes for working with RDF is :class:`~rdflib.graph.Graph`. 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.
RDFLib graphs are not sorted containers; they have ordinary ``set`` operations (e.g. :meth:`~rdflib.Graph.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 `emulate container types <http://docs.python.org/release/2.5.2/ref/sequence-types.html>`_ and are best thought of as a set of 3-item triples:
.. code-block:: text
[
(subject, predicate, object),
(subject1, predicate1, object1),
...
(subjectN, predicateN, objectN)
]
A tiny usage example:
.. code-block:: pycon
>>> import rdflib
>>> g = rdflib.Graph()
>>> result = g.parse("http://www.w3.org/People/Berners-Lee/card")
>>> print("graph has %s statements." % len(g))
graph has 79 statements.
>>> for subj, pred, obj in g:
... if (subj, pred, obj) not in g:
... raise Exception("It better be!")
>>> s = g.serialize(format='n3')
A more extensive example:
.. code-block:: python
from rdflib.graph import Graph
from rdflib import Literal, BNode, Namespace
from rdflib import RDF
g = Graph()
# Bind a few prefix, namespace pairs.
g.bind("dc", "http://http://purl.org/dc/elements/1.1/")
g.bind("foaf", "http://xmlns.com/foaf/0.1/")
# Create a namespace object for the Friend of a friend namespace.
FOAF = Namespace("http://xmlns.com/foaf/0.1/")
# Create an identifier to use as the subject for Donna.
donna = BNode()
# Add triples using store's add method.
g.add((donna, RDF.type, FOAF["Person"]))
g.add((donna, FOAF["nick"], Literal("donna", lang="foo")))
g.add((donna, FOAF["name"], Literal("Donna Fales")))
# 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 its mbox property.
print("--- printing mboxes ---")
for person in g.subjects(RDF.type, FOAF["Person"]):
for mbox in g.objects(person, FOAF["mbox"]):
print(mbox)
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