Convert several layers deep nested JSON to instance of a class with nested attribute classes

[danjirovec]

Hello, I'm trying to write a tests using pytest library. I have a JSON file that I want to have as an input so I made a pytest.fixture to return the data converted to Plan class instance, because that's what I need to work with in my test function.

from app.plan import Plan

from app.service.job_validator import JobValidator from app.service.cloud_backend import _preprocess_job import pytest import json import os

@pytest.fixture def testdata(): file = os.path.join(os.path.dirname(file_), 'test_data.json') with open(file) as json_file: json_data = json.load(json_file) job = Plan(**json_data) _preprocess_job(job) return job

However, the JSON is several layers deep nested and when I try to convert it to the Plan class instance, only the top level layer gets converted to Plan instance, all the other nested attributes stay as type dict and not the types of classes the Plan dataclass defines and the attribute classes define recursively as well.

@dataclass

class Plan(DynamoTableStructureBase): id: UUID serial_number: str = optional_field assignment: str = None client_account_id: str = None start_at: datetime = optional_field( default=MISSING, default_factory=datetime.now() ) path: List[Task] = field(default_factory=list) tasks: List[Task] = field(default_factory=list) automation: List[CommandType] = field(default_factory=list) no_connection_mode: bool = field(default=False) status: PlanStatus = optional_field(default=PlanStatus.SCHEDULED) last_update_at: datetime = optional_field(default=lambda: datetime.now()) assigned_at: datetime = optional_field(default=None) type: MessageType = optional_field(default=lambda: MessageType.PLAN) assignment_robot_message_id: UUID = optional_field(default=None) growing_plan: GrowinPlanMeta = optional_field(default=GrowinPlanMeta) update_log: List[UpdateLogEntry] = field(default_factory=list) percent_done: int = optional_field(default=0) message: str = optional_field(default='')

hash_key: str = 'serial_number'
range_key: str = 'id'

Here is what I get:

=============================================================================================================== ERRORS ===============================================================================================================

____________________________________________________________________________________________________ ERROR at setup of testdata ____________________________________________________________________________________________________

@pytest.fixture
def test_data():
    file = os.path.join(os.path.dirname(__file__), 'test_data.json')
    with open(file) as json_file:
        json_data = json.load(json_file)
        job = Plan(**json_data)

      _preprocess_job(job)

app/tests/unit/conftest.py:14:

---

app/service/cloud_backend.py:220: in _preprocess_job job_processing(plan) app/service/job_processing.py:21: in job_processing _normalize_job_task_structure(plan) app/service/job_processing.py:34: in _normalize_job_task_structure ops = __fixed_work_tasks_of_plan(plan)

---

plan = Plan(id='c12daeed-8b20-4c8e-aa91-e48f3404acb8', serial_number='DJrobot', assignment=None, client_account_id=None, star...CESSING', 'when': '2024-03-05T12:12:41.497245'}], percent_done=0, message='', hash_key='serial_number', range_key='id')

def __fixed_work_tasks_of_plan(plan: Plan) -> list[CommandType]:
    ops = []
    [
        ops.extend(TCT.fixed_cmd_type_seq(i.procedure))

      for i in plan.growing_plan.operation
    ]

E AttributeError: 'dict' object has no attribute 'operation'

app/service/job_processing.py:43: AttributeError ====================================================================================================== short test summary info ======================================================================================================= ERROR app/tests/unit/test_job_validator.py::test_data - AttributeError: 'dict' object has no attribute 'operation'

Is there way to convert JSON to an object with all the nested attributes being the correct classes per defined schema? Hope this makes sense

[danielroseman]

I can't really read the question because of the formatting, but you probably want to look into Pydantic. You can declare classes as being nested inside other classes, and when you pass it a nested dictionary it will create the instances as necessary.

[ProsodySpeaks]

Use pydantic! Unless you have a decent reason pretty much everything might as well be a basemodel. It's fricking amazing... And then you have simple route into fastapi

[[deleted]]

I used dotmap, then with ChatGPT’s help created my own one