error_handling.py

from graphql.core import graphql
from graphql.core.type import (
    GraphQLObjectType,
    GraphQLField,
    GraphQLArgument,
    GraphQLNonNull,
    GraphQLSchema,
    GraphQLString,
)


def raises(*_):
    raise Exception("Throws!")


def resolver(root, args, *_):
    return 'Hello ' + (args['who'] or 'World')


TestSchema = GraphQLSchema(
    query=GraphQLObjectType(
        'Root',
        fields=lambda: {
            'test': GraphQLField(
                GraphQLString,
                args={
                    'who': GraphQLArgument(
                        type=GraphQLString
                    )
                },
                resolver=resolver
            ),
            'thrower': GraphQLField(
                GraphQLNonNull(GraphQLString),
                resolver=raises
            )
        }
    )
)


result = graphql(TestSchema, '{thrower}', None, None, None)


print result.data
print result.errors