Extending a SchemaΒΆ

With GraphQL-core 3 you can also extend a given schema using type extensions. For example, we might want to add a lastName property to our Human data type to retrieve only the last name of the person.

This can be achieved with the graphql.utilities.extend_schema() function as follows:

from graphql import extend_schema, parse

schema = extend_schema(schema, parse("""
    extend type Human {
     lastName: String
    }
    """))

Note that this function expects the extensions as an AST, which we can get using the graphql.language.parse() function. Also note that the extend_schema function does not alter the original schema, but returns a new schema object.

We also need to attach a resolver function to the new field:

def get_last_name(human, info):
    return human['name'].rsplit(None, 1)[-1]

schema.get_type('Human').fields['lastName'].resolve = get_last_name

Now we can query only the last name of a human:

from graphql import graphql_sync

result = graphql_sync(schema, """
    {
      human(id: "1000") {
        lastName
        homePlanet
      }
    }
    """)
print(result)

This query will give the following result:

ExecutionResult(
    data={'human': {'lastName': 'Skywalker', 'homePlanet': 'Tatooine'}},
    errors=None)