Use stockholm.Money in Pydantic models

Money objects can be used in Pydantic (Pydantic>=2.2 supported) models and used with Pydantic's JSON serialization and validation – the same goes for Number and Currency objects as well.

Previously validation of these types required the Pydantic config option arbitrary_types_allowed and JSON serialization with model_dump_json() resulted in an exception. With these updates there's no need for arbitrary_types_allowed and pydantic model's using Money fields can use JSON serialization+deserialization natively.

Specify the stockholm.Money type as the field type and you're good to go.

from pydantic import BaseModel
from stockholm import Money

class Transaction(BaseModel):
    reference: str
    amount: Money

transaction = Transaction(reference="abc123", amount=Money("100.00", "SEK"))
# Transaction(reference='abc123', amount=<stockholm.Money: "100.00 SEK">)

json_data = transaction.model_dump_json()
# '{"reference":"abc123","amount":{"value":"100.00 SEK","units":100,"nanos":0,"currency_code":"SEK"}}'

Transaction.model_validate_json(json_data)
# Transaction(reference='abc123', amount=<stockholm.Money: "100.00 SEK">)

It's also possible to use the stockholm.types Pydantic field types, for example stockholm.types.ConvertibleToMoney, which will automatically coerce input into a Money object.

from pydantic import BaseModel
from stockholm import Money
from stockholm.types import ConvertibleToMoney

class ExampleModel(BaseModel):
    amount: ConvertibleToMoney

example = ExampleModel(amount="4711.50 USD")
# ExampleModel(amount=<stockholm.Money: "4711.50 USD">)

example.model_dump_json()
# '{"amount":{"value":"4711.50 USD","units":4711,"nanos":500000000,"currency_code":"USD"}}'

Other similar field types that can be used on Pydantic fields are:

• stockholm.types.ConvertibleToNumber
• stockholm.types.ConvertibleToMoneyWithRequiredCurrency
• stockholm.types.ConvertibleToCurrency

Note that it's generally recommended to opt for the more strict types (stockholm.Money, stockholm.Number and stockholm.Currency) when possible and the coercion field types should be used with caution and is mainly suited for experimentation and early development.

Related to issue:

• Questions about Pydantic and Unicode symbols #270