[Pydantic subclassing] camelcasing aliases and json dumps #fastapi #pydantic

example.py

# https://github.com/tiangolo/fastapi/issues/413#issuecomment-517504748

# @Rehket for what it's worth, I recommend subclassing BaseModel and using that as the root for all of your API models (to reduce code repetition). For example, I use a base class that mostly looks like this:

import re
from functools import partial
from typing import Any, Dict

from fastapi.encoders import jsonable_encoder
from pydantic import BaseConfig, BaseModel


def snake2camel(snake: str, start_lower: bool = False) -> str:
    camel = snake.title()
    camel = re.sub("([0-9A-Za-z])_(?=[0-9A-Z])", lambda m: m.group(1), camel)
    if start_lower:
        camel = re.sub("(^_*[A-Z])", lambda m: m.group(1).lower(), camel)
    return camel


class APIModel(BaseModel):
    class Config(BaseConfig):
        orm_mode = True
        allow_population_by_alias = True
        alias_generator = partial(snake2camel, start_lower=True)

    def dump_obj(self, **jsonable_encoder_kwargs: Any) -> Dict[str, Any]:
        return jsonable_encoder(self, **jsonable_encoder_kwargs)

# Then I can do

class UserCreate(APIModel):
    user_id: uuid.UUID
    password: str

# and get automatic generation of camelcase aliases, and have the dump_obj method (which generates a more json-dumps-friendly dict than model.dict(), which, for example, doesn't).