Pydantic parameter selection examples.

[downdawn]

Share several ways of writing parameter selection values, which may be useful

1、what goes in and what goes out

from typing import Literal

from pydantic import BaseModel


class User(BaseModel):
    name: str
    gender: Literal["female", "male", "other"]


user = User(name="dylan", gender="female")
print(user.dict())  # {'name': 'dylan', 'gender': 'female'}

2、The input and output are inconsistent, and the output can be customized (simple)

from enum import IntEnum

from pydantic import BaseModel, validator


class GenderEnum(IntEnum):
    female = 0
    male = 1
    other = 2


class User(BaseModel):
    name: str
    gender: GenderEnum

    @validator('gender')
    def validate_gender(cls, v):
        return GenderEnum(v).name


user = User(name="dylan", gender=0)
print(user.dict())  # {'name': 'dylan', 'gender': 'female'}

3、Input and output are inconsistent, output can be customized (complex)

from enum import Enum

from pydantic import BaseModel, root_validator


class Gender(str, Enum):
    female = "it's a female"
    male = "it's a male"
    other = "it's a other"


class User(BaseModel):
    name: str
    gender: str

    @root_validator(pre=True)
    def map_enums(cls, values):
        gender = values.get("gender")
        if gender:
            try:
                values["gender"] = Gender[gender].value
            except Exception:
                raise ValueError(f"Invalid value for gender: {gender}")
        return values


user = User(name="dylan", gender="female")
print(user.dict())  # {'name': 'dylan', 'gender': "it's a female"}