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PyLOD is a Python wrapper for exposing Linked Open Data from public SPARQL-served endpoints.

Project description

PyLOD

PyLOD is a Python wrapper for exposing Linked Open Data from public SPARQL-served endpoints. It acts as an abstraction layer for the retrieval of structured data, such as classes, properties and individuals, without requiring any knowledge of SPARQL.

Getting Started

PyLOD is a minimal module for Python (2.x. and 3.x).

Prerequisites

SPARQLWrapper - SPARQLWrapper is a simple Python wrapper around a SPARQL service to remotelly execute queries.

Installation

  • Manually

  1. Install SPARQLWrapper.
  2. Save PyLOD.py to your project's directory.
  • From PyPi

pip install PyLOD

Usage

1. Import the PyLOD class and create a PyLOD class object.

from PyLOD import PyLOD
pylod = PyLOD()

2. Provide a dictionary of desired namespaces

my_namespaces={
    "dbo": "http://dbpedia.org/ontology/",
    "dbp": "http://dbpedia.org/property/"
}

pylod.namespaces.set_namespaces(my_namespaces)

This step is optional, since PyLOD already incorporates a set of known namespaces. To get the list of defined namespaces, use this:

print(pylod.namespaces.get_namespaces())

3. Define a dictionary of SPARQL endpoints to be queried:

my_endpoints={
    "DBpedia": "http://dbpedia.org/sparql",
    "GeoLinkedData": "http://linkedgeodata.org/sparql"
}

pylod.endpoints.set_endpoints(my_endpoints)

If no endpoints are defined, PyLOD will use a pre-defined set of known endpoints. To get the list of these endpoints, do this:

print(pylod.endpoints.get_endpoints())

4. Use PyLOD's expose functions to retrieve structured data from the endpoints. Set the optional argument limit_per_endpoint to limit the results per endpoint. For example:

# Get entities of type owl:Class
classes = pylod.expose.classes(limit_per_endpoint=100)

# Get the sub-classes of a specific class 
sub_classes = pylod.expose.sub_classes(super_class="dbo:Artist")

# Get instances of a specific class 
instances = pylod.expose.instances_of_class(cls="dbo:Artist", include_subclasses=True, limit_per_endpoint=50)

# Execute custom SPARQL select query to all endpoints
results = pylod.sparql.execute_select_to_all_endpoints(query="SELECT * WHERE {?s ?p ?o}")

Expose functions:

  • classes() - Returns class entities
  • sub_classes() - Returns the sub-classes of a given class
  • super_classes() - Returns the super-classes of a given class
  • equivalent_classes() - Returns the equivalent classes of a given class
  • disjoint_classes() - Returns the disjoint classes of a given class
  • sub_properties() - Returns the sub-properties of a given property
  • super_properties() - Returns the super-properties of a given property
  • triples() - Allows the retrieval of triples within the pattern (subject-predicate-object)
  • subjects() - Returns the subjects of a given predicate-object pair
  • predicates() - Returns the predicates of a given subject-object pair
  • objects() - Returns the objects of a given subject-predicate pair
  • instances_of_class() - Returns instances of a given class type
  • labels() - Returns labels of a given entity, with an optional language argument

SPARQL functions:

  • execute_select() - Allows the execution of a custom SPARQL select query to a given endpoint URL
  • execute_select_to_all_endpoints() - Allows the execution of a custom SPARQL select query to all endpoints defined in pylod.endpoints.get_endpoints()
  • is_active_endpoint() - Checks if a given endpoint URL is alive and responds to SPARQL queries

Documentation

The official webpage - The Docs

Authors

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Applications

PyLOD has been deployed in the following projects:

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