docs/source/SPARQLWrapper-250.png

SPARQL Endpoint interface to Python

Build Status PyPi version

About

SPARQLWrapper is a simple Python wrapper around a SPARQL service to remotely execute your queries. It helps in creating the query invokation and, possibly, convert the result into a more manageable format.

Installation & Distribution

You can install SPARQLWrapper from PyPi:

$ pip install sparqlwrapper

You can install SPARQLWrapper from GitHub:

$ pip install git+https://github.com/rdflib/sparqlwrapper#egg=sparqlwrapper

You can install SPARQLWrapper from Debian:

$ sudo apt-get install python-sparqlwrapper

Note

Be aware that there could be a gap between the latest version of SPARQLWrapper and the version available as Debian package.

Also, the source code of the package can be downloaded in .zip and .tar.gz formats from GitHub SPARQLWrapper releases. Documentation is included in the distribution.

How to use

First steps

The simplest usage of this module looks as follows (using the default, ie, XML return format, and special URI for the SPARQL Service):

from SPARQLWrapper import SPARQLWrapper

queryString = "SELECT * WHERE { ?s ?p ?o. }"
sparql = SPARQLWrapper("http://example.org/sparql")

sparql.setQuery(queryString)

try :
   ret = sparql.query()
   # ret is a stream with the results in XML, see <http://www.w3.org/TR/rdf-sparql-XMLres/>
except :
   deal_with_the_exception()

If SPARQLWrapper("http://example.org/sparql",returnFormat=SPARQLWrapper.JSON) was used, the result would be in JSON format instead of XML.

SELECT example

from SPARQLWrapper import SPARQLWrapper, JSON

sparql = SPARQLWrapper("http://dbpedia.org/sparql")
sparql.setQuery("""
    PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
    SELECT ?label
    WHERE { <http://dbpedia.org/resource/Asturias> rdfs:label ?label }
""")
sparql.setReturnFormat(JSON)
results = sparql.query().convert()

for result in results["results"]["bindings"]:
    print(result["label"]["value"])

print('---------------------------')

for result in results["results"]["bindings"]:
    print('%s: %s' % (result["label"]["xml:lang"], result["label"]["value"]))

ASK example

from SPARQLWrapper import SPARQLWrapper, XML

sparql = SPARQLWrapper("http://dbpedia.org/sparql")
sparql.setQuery("""
    ASK WHERE {
        <http://dbpedia.org/resource/Asturias> rdfs:label "Asturias"@es
    }
""")
sparql.setReturnFormat(XML)
results = sparql.query().convert()
print(results.toxml())

CONSTRUCT example

from SPARQLWrapper import SPARQLWrapper, RDFXML
from rdflib import Graph

sparql = SPARQLWrapper("http://dbpedia.org/sparql")

sparql.setQuery("""
    PREFIX dbo: <http://dbpedia.org/ontology/>
    PREFIX schema: <http://schema.org/>

    CONSTRUCT {
      ?lang a schema:Language ;
      schema:alternateName ?iso6391Code .
    }
    WHERE {
      ?lang a dbo:Language ;
      dbo:iso6391Code ?iso6391Code .
      FILTER (STRLEN(?iso6391Code)=2) # to filter out non-valid values
    }
""")

sparql.setReturnFormat(RDFXML)
results = sparql.query().convert()
print(results.serialize(format='xml'))

DESCRIBE example

from SPARQLWrapper import SPARQLWrapper, N3
from rdflib import Graph

sparql = SPARQLWrapper("http://dbpedia.org/sparql")

sparql.setQuery("""
    DESCRIBE <http://dbpedia.org/resource/Asturias>
""")

sparql.setReturnFormat(N3)
results = sparql.query().convert()
g = Graph()
g.parse(data=results, format="n3")
print(g.serialize(format='n3'))

SPARQL UPDATE example

from SPARQLWrapper import SPARQLWrapper, POST, DIGEST

sparql = SPARQLWrapper("https://example.org/sparql-auth")

sparql.setHTTPAuth(DIGEST)
sparql.setCredentials("login", "password")
sparql.setMethod(POST)

sparql.setQuery("""
WITH <http://example.graph>
DELETE
{ <http://dbpedia.org/resource/Asturias> rdfs:label "Asturies"@ast }
""")

results = sparql.query()
print results.response.read()

SPARQLWrapper2 example

There is also a SPARQLWrapper2 class that works with JSON SELECT results only and wraps the results to make processing of average queries a bit simpler.

from SPARQLWrapper import SPARQLWrapper2

sparql = SPARQLWrapper2("http://dbpedia.org/sparql")
sparql.setQuery("""
    PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
    SELECT ?label
    WHERE { <http://dbpedia.org/resource/Asturias> rdfs:label ?label }
""")

for result in sparql.query().bindings:
    print('%s: %s' % (result["label"].lang, result["label"].value))

Return formats

The expected return formats differs from the query type (SELECT, ASK, CONSTRUCT, DESCRIBE…).

Note

From the SPARQL specification, The response body of a successful query operation with a 2XX response is either:

  • SELECT and ASK: a SPARQL Results Document in XML, JSON, or CSV/TSV format.
  • DESCRIBE and CONSTRUCT: an RDF graph serialized, for example, in the RDF/XML syntax, or an equivalent RDF graph serialization.

The package, though it does not contain a full SPARQL parser, makes an attempt to determine the query type when the query is set. This should work in most of the cases (but there is a possibility to set this manually, in case something goes wrong).

Automatic conversion of the results

To make processing somewhat easier, the package can do some conversions automatically from the return result. These are:

  • for XML, the xml.dom.minidom is used to convert the result stream into a Python representation of a DOM tree.
  • for JSON, the json package to generate a Python dictionary. Until version 1.3.1, the simplejson package was used.
  • for CSV or TSV, a simple string.
  • For RDF/XML and JSON-LD, the RDFLib package is used to convert the result into a Graph instance.
  • For RDF Turtle/N3, a simple string.

There are two ways to generate this conversion:

  • use ret.convert() in the return result from sparql.query() in the code above
  • use sparql.queryAndConvert() to get the converted result right away if the intermediate stream is not used

For example, in the code below:

try :
    sparql.setReturnFormat(SPARQLWrapper.JSON)
    ret = sparql.query()
    dict = ret.convert()
except:
    deal_with_the_exception()

the value of dict is a Python dictionary of the query result, based on the SPARQL Query Results JSON Format.

Partial interpretation of the results

A further help is to offer an extra, partial interpretation of the results, again to cover most of the practical use cases. Based on the SPARQL Query Results JSON Format, the SPARQLWrapper.SmartWrapper.Bindings class can perform some simple steps in decoding the JSON return results. If SPARQLWrapper.SmartWrapper.SPARQLWrapper2 is used instead of SPARQLWrapper.Wrapper.SPARQLWrapper, this result format is generated. Note that this relies on a JSON format only, ie, it has to be checked whether the SPARQL service can return JSON or not.

Here is a simple code that makes use of this feature:

from SPARQLWrapper import SPARQLWrapper2

queryString = "SELECT ?subj ?prop WHERE { ?subj ?prop ?o. }"

sparql = SPARQLWrapper2("http://example.org/sparql")

sparql.setQuery(queryString)
try :
    ret = sparql.query()
    print ret.variables  # this is an array consisting of "subj" and "prop"
    for binding in ret.bindings :
        # each binding is a dictionary. Let us just print the results
        print "%s: %s (of type %s)" % ("s",binding[u"subj"].value,binding[u"subj"].type)
        print "%s: %s (of type %s)" % ("p",binding[u"prop"].value,binding[u"prop"].type)
except:
    deal_with_the_exception()

To make this type of code even easier to realize, the [] and in operators are also implemented on the result of SPARQLWrapper.SmartWrapper.Bindings. This can be used to check and find a particular binding (ie, particular row in the return value). This features becomes particularly useful when the OPTIONAL feature of SPARQL is used. For example:

from SPARQLWrapper import SPARQLWrapper2

queryString = "SELECT ?subj ?o ?opt WHERE { ?subj <http://a.b.c> ?o. OPTIONAL { ?subj <http://d.e.f> ?opt }}"

sparql = SPARQLWrapper2("http://example.org/sparql")

sparql.setQuery(queryString)
try :
    ret = sparql.query()
    print ret.variables  # this is an array consisting of "subj", "o", "opt"
    if (u"subj",u"prop",u"opt") in ret :
       # there is at least one binding covering the optional "opt", too
       bindings = ret[u"subj",u"o",u"opt"]
       # bindings is an array of dictionaries with the full bindings
       for b in bindings :
           subj = b[u"subj"].value
           o    = b[u"o"].value
           opt  = b[u"opt"].value
           # do something nice with subj, o, and opt
    # another way of accessing to values for a single variable:
    # take all the bindings of the "subj"
    subjbind = ret.getValues(u"subj") # an array of Value instances
    ...
except:
    deal_with_the_exception()

GET or POST

By default, all SPARQL services are invoked using HTTP GET verb. However, POST might be useful if the size of the query extends a reasonable size; this can be set in the query instance.

Note that some combination may not work yet with all SPARQL processors (e.g., there are implementations where POST + JSON return does not work). Hopefully, this problem will eventually disappear.

Database management systems

Introduction

From SPARQL 1.1 Specification:

The response body of a successful query operation with a 2XX response is either:

  • SELECT and ASK: a SPARQL Results Document in XML, JSON, or CSV/TSV format.
  • DESCRIBE and CONSTRUCT: an RDF graph serialized, for example, in the RDF/XML syntax, or an equivalent RDF graph serialization.

The fact is that the parameter key for the choice of the output format is not defined. Virtuoso uses format, joseki/fuseki uses output, rasqual seems to use results, etc… Also, in some cases HTTP Content Negotiation can/must be used.

ClioPatria

Website:The SWI-Prolog Semantic Web Server
Documentation:Search ‘sparql’ in http://cliopatria.swi-prolog.org/help/http.
Uses:Parameters and Content Negotiation.
Parameter key:format.
Parameter value:
 MUST be one of these values: rdf+xml, json, csv, application/sparql-results+xml or application/sparql-results+json.

Fuseki

Website:Fuseki (formerly there was Joseki)
Uses:Parameters and Content Negotiation.
Parameter key:format or output (Fuseki 1, Fuseki 2).
JSON-LD (application/ld+json):
 supported (in CONSTRUCT and DESCRIBE).

Eclipse RDF4J

Website:Eclipse RDF4J (formerly known as OpenRDF Sesame)
Documentation:https://rdf4j.eclipse.org/documentation/rest-api/#the-query-operation, https://rdf4j.eclipse.org/documentation/rest-api/#content-types
Uses:Only content negotiation (no URL parameters).
Parameter:If an unexpected parameter is used, the server ignores it.
JSON-LD (application/ld+json):
 supported (in CONSTRUCT and DESCRIBE).
  • SELECT
    • application/sparql-results+xml (DEFAULT if Accept: */* is sent))
    • application/sparql-results+json (also application/json)
    • text/csv
    • text/tab-separated-values
    • Other values: application/x-binary-rdf-results-table
  • ASK
    • application/sparql-results+xml (DEFAULT if Accept: */* is sent))
    • application/sparql-results+json
    • Other values: text/boolean
    • Not supported: text/csv
    • Not supported: text/tab-separated-values
  • CONSTRUCT
    • application/rdf+xml
    • application/n-triples (DEFAULT if Accept: */* is sent)
    • text/turtle
    • text/n3
    • application/ld+json
    • Other acceptable values: application/n-quads, application/rdf+json, application/trig, application/trix, application/x-binary-rdf
    • text/plain (returns application/n-triples)
    • text/rdf+n3 (returns text/n3)
    • text/x-nquads (returns application/n-quads)
  • DESCRIBE
    • application/rdf+xml
    • application/n-triples (DEFAULT if Accept: */* is sent)
    • text/turtle
    • text/n3
    • application/ld+json
    • Other acceptable values: application/n-quads, application/rdf+json, application/trig, application/trix, application/x-binary-rdf
    • text/plain (returns application/n-triples)
    • text/rdf+n3 (returns text/n3)
    • text/x-nquads (returns application/n-quads)

RASQAL

Website:RASQAL
Documentation:http://librdf.org/rasqal/roqet.html
Parameter key:results.
JSON-LD (application/ld+json):
 NOT supported.

Uses roqet as RDF query utility (see http://librdf.org/rasqal/roqet.html) For variable bindings, the values of FORMAT vary upon what Rasqal supports but include simple for a simple text format (default), xml for the SPARQL Query Results XML format, csv for SPARQL CSV, tsv for SPARQL TSV, rdfxml and turtle for RDF syntax formats, and json for a JSON version of the results.

For RDF graph results, the values of FORMAT are ntriples (N-Triples, default), rdfxml-abbrev (RDF/XML Abbreviated), rdfxml (RDF/XML), turtle (Turtle), json (RDF/JSON resource centric), json-triples (RDF/JSON triples) or rss-1.0 (RSS 1.0, also an RDF/XML syntax).

Marklogic

Website:Marklogic
Uses:Only content negotiation (no URL parameters).
JSON-LD (application/ld+json):
 NOT supported.

You can use following methods to query triples:

  • SPARQL mode in Query Console. For details, see Querying Triples with SPARQL
  • XQuery using the semantics functions, and Search API, or a combination of XQuery and SPARQL. For details, see Querying Triples with XQuery or JavaScript.
  • HTTP via a SPARQL endpoint. For details, see Using Semantics with the REST Client API.

Formats are specified as part of the HTTP Accept headers of the REST request. When you query the SPARQL endpoint with REST Client APIs, you can specify the result output format (See https://docs.marklogic.com/guide/semantics/REST#id_54258. The response type format depends on the type of query and the MIME type in the HTTP Accept header.

This table describes the MIME types and Accept Header/Output formats (MIME type) for different types of SPARQL queries. (See https://docs.marklogic.com/guide/semantics/REST#id_54258 and https://docs.marklogic.com/guide/semantics/loading#id_70682)

  • SELECT
    • application/sparql-results+xml
    • application/sparql-results+json
    • text/html
    • text/csv
  • ASK queries return a boolean (true or false).
  • CONSTRUCT or DESCRIBE
    • application/n-triples
    • application/rdf+json
    • application/rdf+xml
    • text/turtle
    • text/n3
    • application/n-quads
    • application/trig

AllegroGraph

Website:AllegroGraph
Documentation:https://franz.com/agraph/support/documentation/current/http-protocol.html
Uses:Only content negotiation (no URL parameters).
Parameter:The server always looks at the Accept header of a request, and tries to generate a response in the format that the client asks for. If this fails, a 406 response is returned. When no Accept, or an Accept of / is specified, the server prefers text/plain, in order to make it easy to explore the interface from a web browser.
JSON-LD (application/ld+json):
 NOT supported.
  • SELECT
    • application/sparql-results+xml (DEFAULT if Accept: / is sent)
    • application/sparql-results+json (and application/json)
    • text/csv
    • text/tab-separated-values
    • OTHERS: application/sparql-results+ttl, text/integer, application/x-lisp-structured-expression, text/table, application/processed-csv, text/simple-csv, application/x-direct-upis
  • ASK
    • application/sparql-results+xml (DEFAULT if Accept: / is sent)
    • application/sparql-results+json (and application/json)
    • Not supported: text/csv
    • Not supported: text/tab-separated-values
  • CONSTRUCT
    • application/rdf+xml (DEFAULT if Accept: / is sent)
    • text/rdf+n3
    • OTHERS: text/integer, application/json, text/plain, text/x-nquads, application/trix, text/table, application/x-direct-upis
  • DESCRIBE
    • application/rdf+xml (DEFAULT if Accept: / is sent)
    • text/rdf+n3

4store

Website:4store
Documentation:https://4store.danielknoell.de/trac/wiki/SparqlServer/
Uses:Parameters and Content Negotiation.
Parameter key:output.
Parameter value:
 alias. If an unexpected alias is used, the server is not working properly.
JSON-LD (application/ld+json):
 NOT supported.
  • SELECT
    • application/sparql-results+xml (alias xml) (DEFAULT if Accept: / is sent))
    • application/sparql-results+json or application/json (alias json)
    • text/csv (alias csv)
    • text/tab-separated-values (alias tsv). Returns “text/plain” in GET.
    • Other values: text/plain, application/n-triples
  • ASK
    • application/sparql-results+xml (alias xml) (DEFAULT if Accept: / is sent))
    • application/sparql-results+json or application/json (alias json)
    • text/csv (alias csv)
    • text/tab-separated-values (alias tsv). Returns “text/plain” in GET.
    • Other values: text/plain, application/n-triples
  • CONSTRUCT
    • application/rdf+xml (alias xml) (DEFAULT if Accept: / is sent)
    • text/turtle (alias “text”)
  • DESCRIBE
    • application/rdf+xml (alias xml) (DEFAULT if Accept: / is sent)
    • text/turtle (alias “text”)
Valid alias for SELECT and ASK:
 “json”, “xml”, csv”, “tsv” (also “text” and “ascii”)
Valid alias for DESCRIBE and CONSTRUCT:
 “xml”, “text” (for turtle)

Blazegraph

Website:Blazegraph (Formerly known as Bigdata) & NanoSparqlServer
Documentation:https://wiki.blazegraph.com/wiki/index.php/REST_API#SPARQL_End_Point
Uses:Parameters and Content Negotiation.
Parameter key:format (available since version 1.4.0). Setting this parameter will override any Accept Header that is present
Parameter value:
 alias. If an unexpected alias is used, the server is not working properly.
JSON-LD (application/ld+json):
 NOT supported.
  • SELECT
    • application/sparql-results+xml (alias xml) (DEFAULT if Accept: / is sent))
    • application/sparql-results+json or application/json (alias json)
    • text/csv
    • text/tab-separated-values
    • Other values: application/x-binary-rdf-results-table
  • ASK
    • application/sparql-results+xml (alias xml) (DEFAULT if Accept: / is sent))
    • application/sparql-results+json or application/json (alias json)
  • CONSTRUCT
    • application/rdf+xml (alias xml) (DEFAULT if Accept: / is sent)
    • text/turtle (returns text/n3)
    • text/n3
  • DESCRIBE
    • application/rdf+xml (alias xml) (DEFAULT if Accept: / is sent)
    • text/turtle (returns text/n3)
    • text/n3
Valid alias for SELECT and ASK:
 “xml”, “json”
Valid alias for DESCRIBE and CONSTRUCT:
 “xml”, “json” (but it returns unexpected “application/sparql-results+json”)

GraphDB

Website:GraphDB, formerly known as OWLIM (OWLIM-Lite, OWLIM-SE)
Documentation:http://graphdb.ontotext.com/documentation/free/
Uses:Only content negotiation (no URL parameters).
Note:If the Accept value is not within the expected ones, the server returns a 406 “No acceptable file format found.”
JSON-LD (application/ld+json):
 supported (in CONSTRUCT and DESCRIBE).
  • SELECT
    • application/sparql-results+xml, application/xml (.srx file)
    • application/sparql-results+json, application/json (.srj file)
    • text/csv (DEFAULT if Accept: / is sent)
    • text/tab-separated-values
  • ASK
    • application/sparql-results+xml, application/xml (.srx file)
    • application/sparql-results+json (DEFAULT if Accept: / is sent), application/json (.srj file)
    • NOT supported: text/csv, text/tab-separated-values
  • CONSTRUCT
    • application/rdf+xml, application/xml (.rdf file)
    • text/turtle (.ttl file)
    • application/n-triples (.nt file) (DEFAULT if Accept: / is sent)
    • text/n3, text/rdf+n3 (.n3 file)
    • application/ld+json (.jsonld file)
  • DESCRIBE
    • application/rdf+xml, application/xml (.rdf file)
    • text/turtle (.ttl file)
    • application/n-triples (.nt file) (DEFAULT if Accept: / is sent)
    • text/n3, text/rdf+n3 (.n3 file)
    • application/ld+json (.jsonld file)

Stardog

Website:Stardog
Documentation:https://www.stardog.com/docs/#_http_headers_content_type_accept (looks outdated)
Uses:Only content negotiation (no URL parameters).
Parameter key:If an unexpected parameter is used, the server ignores it.
JSON-LD (application/ld+json):
 supported (in CONSTRUCT and DESCRIBE).
  • SELECT
    • application/sparql-results+xml (DEFAULT if Accept: / is sent)
    • application/sparql-results+json
    • text/csv
    • text/tab-separated-values
    • Other values: application/x-binary-rdf-results-table
  • ASK
    • application/sparql-results+xml (DEFAULT if Accept: / is sent)
    • application/sparql-results+json
    • Other values: text/boolean
    • Not supported: text/csv
    • Not supported: text/tab-separated-values
  • CONSTRUCT
    • application/rdf+xml
    • text/turtle (DEFAULT if Accept: / is sent)
    • text/n3
    • application/ld+json
    • Other acceptable values: application/n-triples, application/x-turtle, application/trig, application/trix, application/n-quads
  • DESCRIBE
    • application/rdf+xml
    • text/turtle (DEFAULT if Accept: / is sent)
    • text/n3
    • application/ld+json
    • Other acceptable values: application/n-triples, application/x-turtle, application/trig, application/trix, application/n-quads

Development

Requirements

The RDFLib package is used for RDF parsing.

This package is imported in a lazy fashion, ie, only when needed. Ie, if the user never intends to use the RDF format, the RDFLib package is not imported and the user does not have to install it.

Source code

The source distribution contains:

  • SPARQLWrapper: the Python package. You should copy the directory somewhere into your PYTHONPATH. Alternatively, you can also run the distutils scripts: python setup.py install
  • test: some unit and integrations tests. In order to run the tests some packages have to be installed before. So please install the packages listed in requirements.development.txt: pip install -r requirements.development.txt
  • scripts: some scripts to run the package against some SPARQL endpoints.
  • docs: the documentation.
  • custom_fixers: 2to3 custom_fixer in order to fix an issue with urllib2._opener.

Community

Community support is available through the developer’s discussion group rdflib-dev. The archives. from the old mailing list are still available.

License

The SPARQLWrapper package is licensed under W3C license.

Acknowledgement

The package was greatly inspired by Lee Feigenbaum’s similar package for Javascript.

Developers involved:

Organizations involved: