Pydantic model with optional fields

product_model_optionals.py

from enum import Enum
from typing import Optional

import pydantic.main
from pydantic import Field, BaseModel


class AllOptionalMetaclass(pydantic.main.ModelMetaclass):
    ....

    
class SizeEnum(str, Enum):
    SMALL = "Small"
    MEDIUM = "Medium"
    LARGE = "Large"


class Product(BaseModel, metaclass=AllOptionalMetaclass):
    name: str = Field(description="The name of the product")
    price: Optional[float] = Field(
        gt=0,
        description="The price of the product (in euro)",
    )
    quantity: Optional[int] = Field(
        1,
        gt=0,
        description="The available quantity of the product",
    )
    product_size: Optional[SizeEnum] = Field(
        SizeEnum.SMALL,
        description="The size of the product",
    )

    def foo(self, arg: str) -> str:
        return self.name + arg


# Example d'utilisation sans argument
print(Product())
# name=None price=None quantity=1 product_size=<SizeEnum.SMALL: 'Small'>

# Example d'utilisation avec explicitement la valeur None
print(Product(name="Car", quantity=None))
# name='Car' price=None quantity=None product_size=<SizeEnum.SMALL: 'Small'>

# Example d'utilisation avec un paramètre invalide
print(Product(quantity=0))
# Traceback (most recent call last):
#   ...
# pydantic.error_wrappers.ValidationError: 1 validation error for Product
# quantity
#   ensure this value is greater than 0 (type=value_error.number.not_gt; limit_value=0)