Use pydantic with django jsonfield and custom classes

1json_pydantic_django.py

import json
from fractions import Fraction
from pprint import pprint
from django.core import exceptions
from django.contrib.postgres.fields import JSONField
from psycopg2.extras import Json

import orjson
from pydantic.json import custom_pydantic_encoder

ENCODERS = {
    Fraction: str,
    Color: str
}


class MyEncoder(json.JSONEncoder):

    def default(self, obj):
        return custom_pydantic_encoder(ENCODERS, obj)


def pydantic_json_dumps(v):
    """
    Use in Config: json_dumps = pydantic_json_dumps
    :param v: 
    :return:
    """
    return json.dumps(v, cls=MyEncoder)


class JsonAdapter(Json):
    """
    Customized psycopg2.extras.Json to allow for a custom encoder.
    """
    def __init__(self, adapted, dumps=None, encoder=None):
        self.encoder = encoder
        super().__init__(adapted, dumps=dumps)

    def dumps(self, obj):
        return pydantic_json_dumps(obj)


class PydanticJSONField(JSONField):

    def validate(self, value, model_instance):
        super().validate(value, model_instance)
        try:
            pydantic_json_dumps(value)
        except TypeError:
            raise exceptions.ValidationError(
                self.error_messages['invalid'],
                code='invalid',
                params={'value': value},
            )

    def get_prep_value(self, value):
        if value is not None:
            return JsonAdapter(value, encoder=self.encoder)
        return value
      
      
def orjson_dumps(v, *, default):
    # faster decoder
    # https://pydantic-docs.helpmanual.io/usage/exporting_models/
    # orjson.dumps returns bytes, to match standard json.dumps we need to decode
    # in Config use json_dumps = orjson_dumps
    try:
        return orjson.dumps(v, default=default).decode()
    except Exception as e:
        return pydantic_json_dumps(v)

basemodel.py

class BaseEntity(BaseModel):
    class Config:
        extra = Extra.ignore
        json_loads = orjson.loads
        json_dumps = orjson_dumps
        use_enum_values = True

use PydanticJSONField for django model