Loading and saving RDF

Reading an n-triples file

RDF data has various syntaxes (xml, n3, ntriples, trix, JSON-LD, etc) that you might want to read. The simplest format is ntriples, a line-based format. Create the file demo.nt in the current directory with these two lines:

<http://bigasterisk.com/foaf.rdf#drewp> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://xmlns.com/foaf/0.1/Person> .
<http://bigasterisk.com/foaf.rdf#drewp> <http://example.com/says> "Hello world" .

You need to tell RDFLib what format to parse, use the format keyword-parameter to parse(), you can pass either a mime-type or the name (a list of available parsers is available). If you are not sure what format your file will be, you can use rdflib.util.guess_format() which will guess based on the file extension.

In an interactive python interpreter, try this:

from rdflib import Graph

g = Graph()
g.parse("demo.nt", format="nt")

print(len(g)) # prints 2

import pprint
for stmt in g:

# prints :
 rdflib.term.Literal('Hello world'))

The final lines show how RDFLib represents the two statements in the file. The statements themselves are just length-3 tuples; and the subjects, predicates, and objects are all rdflib types.

Reading remote graphs

Reading graphs from the net is just as easy:

# prints 42

The format defaults to xml, which is the common format for .rdf files you’ll find on the net.

RDFLib will also happily read RDF from any file-like object, i.e. anything with a .read() method.