Part 5: Using Python dataclasses

If you are not a developer, you can skip this section.

If you are a developer and favor a language other than python, you may still be interested in this section. The use of generated code is an optional but convenient part of LinkML. We are actively adding support for other languages.

Generating a Python datamodel

For illustration, we will take the schema we developed in the last section:

personinfo.yaml:

id: https://w3id.org/linkml/examples/personinfo
name: personinfo
prefixes:                                  ## Note are adding 3 new ones here
  linkml: https://w3id.org/linkml/
  schema: http://schema.org/
  personinfo: https://w3id.org/linkml/examples/personinfo/
  ORCID: https://orcid.org/
imports:
  - linkml:types
default_range: string
  
classes:
  Person:
    class_uri: schema:Person              ## reuse schema.org vocabulary
    attributes:
      id:
        identifier: true
      full_name:
        required: true
        description:
          name of the person
        slot_uri: schema:name             ## reuse schema.org vocabulary
      aliases:
        multivalued: true
        description:
          other names for the person
      phone:
        pattern: "^[\\d\\(\\)\\-]+$"
        slot_uri: schema:telephone       ## reuse schema.org vocabulary
      age:
        range: integer
        minimum_value: 0
        maximum_value: 200
    id_prefixes:
      - ORCID
  Container:
    attributes:
      persons:
        multivalued: true
        inlined_as_list: true
        range: Person

We can use a script that is distributed with LinkML to generate a python dataclasses model:

gen-python personinfo.yaml > personinfo.py

This creates a python datamodel:

@dataclass
class Person(NamedThing):
    """
    A person (alive, dead, undead, or fictional).
    """
    id: Union[str, PersonId] = None
    full_name: Optional[str] = None
    ...

Note you don’t need to directly view the python - but your favorite IDE should be able to autocomplete and type check as expected

You can now write code like:

test.py:

from personinfo import Person

p1 = Person(id='ORCID:9876', full_name='Lex Luthor')
print(p1)

run this:

python test.py

Outputs:

Person(id='ORCID:9876', full_name='Lex Luthor', aliases=[], phone=None, age=None)

Hurray! Perhaps this is not very impressive in itself, but having an object model that is guaranteed to be in sync with your data model can help with productivity and robustness of code.

The LinkML runtime

The LinkML runtime is a separate python library that provides methods needed by your generated datamodel classes, and utilities for converting your python objects into YAML, JSON, RDF, and TSV:

test_runtime.py:

from linkml_runtime.dumpers import json_dumper
from personinfo import Person

p1 = Person(id='ORCID:9876', full_name='Lex Luthor', aliases=["Bad Guy"])
print(json_dumper.dumps(p1))
python test_runtime.py

Outputs:

{
  "id": "ORCID:9876",
  "full_name": "Lex Luthor",
  "aliases": [
    "Bad Guy"
  ],
  "@type": "Person"
}

Alternatives

Further reading

Next

Next we will look at the enumerations feature of LinkML