from datetime import datetime
import ujson
from pydantic import BaseModel

class User(BaseModel):
    id: int
    name = 'John Doe'
    signup_ts: datetime = None

    class Config:
        json_loads = ujson.loads

user = User.parse_raw('{"id": 123, "signup_ts": 1234567890, "name": "John Doe"}')
print(user)
#> User id=123 signup_ts=datetime.datetime(2009, 2, 13, 23, 31, 30, tzinfo=datetime.timezone.utc) name='John Doe'