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A module for ontology-oriented programming in Python: load OWL 2.0 ontologies as Python objects, modify them, save to OWL XML, and perform reasoning via HermiT. It can also generate dialog boxes for editing instances.

Project description

Owlready (previously named Ontopy) is a module for ontology-oriented programming in Python 3.

Note: Owlready is deprecated in favor to the new version, Owlready2: (development version) (stable version)

Owlready can:

  • Import and export OWL 2.0 ontologies in the OWL/XML format (other file formats are not yet supported).

  • Manipulates ontology classes, instances and properties transparently, as if they were normal Python objects.

  • Add Python methods to ontology classes.

  • Perform automatic classification of classes and instances, using the HermiT reasoner.

  • Automatically generate dialog boxes for editing ontology instances, using Editobj3.

Owlready has been created by Jean-Baptiste Lamy at the LIMICS reseach lab. It is available under the GNU LGPL licence v3. If you use Owlready in scientific works, please cite the following article:

Lamy JB. Owlready: Ontology-oriented programming in Python with automatic classification and high level constructs for biomedical ontologies. Artificial Intelligence In Medicine 2017;80C:11-28

In case of troubles, questions or comments, please use this Forum/Mailing list:

What can I do with Owlready?

Load an ontology from a local repository, or from Internet:

>>> from owlready import *
>>> onto_path.append("/path/to/your/local/ontology/repository")
>>> onto = get_ontology("")
>>> onto.load()

Create new classes in the ontology, possibly mixing OWL restrictions and Python methods:

>>> class NonVegetarianPizza(onto.Pizza):
...   equivalent_to = [
...     onto.Pizza
...   & ( restriction("has_topping", SOME, onto.MeatTopping)
...     | restriction("has_topping", SOME, onto.FishTopping)
...     ) ]
...   def eat(self): print("Beurk! I'm vegetarian!")

Access ontology class, and create new instances / individuals:

>>> onto.Pizza
>>> test_pizza = onto.Pizza("test_pizza_owl_identifier")
>>> test_pizza.has_topping = [ onto.CheeseTopping(),
...                            onto.TomatoTopping(),
...                            onto.MeatTopping  () ]

Export to OWL/XML file:


Perform reasoning, and classify instances and classes:

>>> test_pizza.__class__

>>> # Execute HermiT and reparent instances and classes
>>> onto.sync_reasoner()

>>> test_pizza.__class__
Beurk! I'm vegetarian !

For more documentation, look at the doc/ and doc/examples/ directories in the source.



  • Fix sync_reasonner and Hermit call under windows (thanks Clare Grasso)


  • Add warnings

  • Accepts ontologies files that do not ends with ‘.owl’

  • Fix a bug when loading ontologies including concept without a ‘#’ in their IRI


  • Add link to Owlready2 and Nabble forum/mailing list

  • Add load_ontology_from_file()

  • Add unload_all_ontologies()

  • Remove debug file /tmp/sortie_hermit.txt

  • Add Artificial Intelligence In Medicine scientific article in doc and Readme

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