@Jsonize#

Generate to_dict() and to_json() that serialize a class’s declared fields to JSON-native forms — coercing the types json.dumps can’t handle on its own.

The problem it solves#

json.dumps(obj) raises on a plain object, and even vars(obj) fails once a field holds a datetime, UUID, Decimal, Enum, or bytes. Hand-writing a to_dict that walks every field and coerces those types is exactly the boilerplate inito exists to remove. @Jsonize derives it from the class’s annotations, once.

Usage#

import datetime
import uuid

from inito import Data, Jsonize


@Jsonize
@Data
class Event:
    id: uuid.UUID
    when: datetime.datetime
    name: str = ""


event = Event(uuid.uuid4(), datetime.datetime.now(datetime.timezone.utc), "launch")

event.to_dict()   # {"id": "…", "when": "2026-07-13T05:30:00+00:00", "name": "launch"}
event.to_json()   # '{"id": "…", "when": "…", "name": "launch"}'
event.to_json(indent=2, sort_keys=True)   # kwargs are forwarded to json.dumps

What it generates#

  • to_dict(self) -> dict[str, Any] — every declared field, each value coerced to a JSON-native form (see the table). The field → key mapping is fixed at decoration time; only the per-value coercion runs at call time (a field’s runtime value type isn’t knowable earlier).

  • to_json(self, **kwargs) -> str — json.dumps(self.to_dict(), **kwargs); any keyword arguments (indent, sort_keys, …) pass straight through.

Type coercions#

Value type

Serialized as

str / int / float / bool / None

unchanged

datetime / date / time

ISO 8601 string (.isoformat())

uuid.UUID

string

decimal.Decimal

string (no precision loss)

enum.Enum

its .value (recursively)

bytes / bytearray

base64 string

os.PathLike (e.g. pathlib.Path)

string

mapping

{str(key): serialized(value)}

sequence / set

list of serialized items

object with to_dict() (e.g. nested @Jsonize)

that object’s dict

anything else

str(value)

Nest @Jsonize on your nested types so they serialize structurally; an undecorated object falls back to str(...).

Type checking#

The bundled mypy plugin and inito-stubgen both expose to_dict/to_json, so mypy --strict and pyright see them with the right signatures.

Use with FastAPI#

A plain inito object isn’t a Pydantic model, so return the serialized form from a handler:

@app.get("/events/{event_id}")
async def read_event(event_id: int) -> dict:
    return store.get(event_id).to_dict()

Options#

Option

Default

Effect

(none yet)

@Jsonize and @Jsonize() are equivalent

See also#