ormar/docs/fields/pydantic-fields.md

Pydantic only fields

Ormar allows you to declare normal pydantic fields in its model, so you have access to all basic and custom pydantic fields like str, int, HttpUrl, PaymentCardNumber etc.

You can even declare fields leading to nested pydantic only Models, not only single fields.

Since those fields are not stored in database (that's the whole point of those fields), you have to provide a meaningful value for them, either by setting a default one or providing one during model initialization.

If ormar cannot resolve the value for pydantic field it will fail during loading data from the database, with missing required value for declared pydantic field.

Options to provide a value are described below.

Of course you can combine few or all of them in one model.

Optional field

If you set a field as Optional, it defaults to None if not provided and that's exactly what's going to happen during loading from database.

base_ormar_config = ormar.OrmarConfig(
    metadata=sqlalchemy.MetaData(),
    database=databases.Database(DATABASE_URL),
)


class ModelTest(ormar.Model):
    ormar_config = base_ormar_config.copy()

    id: int = ormar.Integer(primary_key=True)
    name: str = ormar.String(max_length=200)
    number: Optional[PaymentCardNumber]

test = ModelTest(name="Test")
assert test.name == "Test"
assert test.number is None
test.number = "123456789015"

await test.save()
test_check = await ModelTest.objects.get()

assert test_check.name == "Test"
# after load it's back to None
assert test_check.number is None

Field with default value

By setting a default value, this value will be set on initialization and database load. Note that setting a default to None is the same as setting the field to Optional.

base_ormar_config = ormar.OrmarConfig(
    metadata=sqlalchemy.MetaData(),
    database=databases.Database(DATABASE_URL),
)


class ModelTest(ormar.Model):
    ormar_config = base_ormar_config.copy()

    id: int = ormar.Integer(primary_key=True)
    name: str = ormar.String(max_length=200)
    url: HttpUrl = "https://www.example.com"

test = ModelTest(name="Test")
assert test.name == "Test"
assert test.url == "https://www.example.com"

test.url = "https://www.sdta.ada.pt"
assert test.url == "https://www.sdta.ada.pt"

await test.save()
test_check = await ModelTest.objects.get()

assert test_check.name == "Test"
# after load it's back to default
assert test_check.url == "https://www.example.com"

Default factory function

By setting a default_factory function, this result of the function call will be set on initialization and each database load.

from pydantic import Field, PaymentCardNumber
# ...


base_ormar_config = ormar.OrmarConfig(
    metadata=sqlalchemy.MetaData(),
    database=databases.Database(DATABASE_URL),
)


CARD_NUMBERS = [
    "123456789007",
    "123456789015",
    "123456789023",
    "123456789031",
    "123456789049",
]


def get_number():
    return random.choice(CARD_NUMBERS)


class ModelTest2(ormar.Model):
    ormar_config = base_ormar_config.copy()

    id: int = ormar.Integer(primary_key=True)
    name: str = ormar.String(max_length=200)
    # note that you do not call the function, just pass reference
    number: PaymentCardNumber = Field(default_factory=get_number)

# note that you still CAN provide a value 
test = ModelTest2(name="Test2", number="4000000000000002")
assert test.name == "Test2"
assert test.number == "4000000000000002"

await test.save()
test_check = await ModelTest2.objects.get()

assert test_check.name == "Test2"
# after load value is set to be one of the CARD_NUMBERS
assert test_check.number in CARD_NUMBERS
assert test_check.number != test.number

Custom setup in __init__

You can provide a value for the field in your __init__() method before calling a super() init method.

from pydantic import BaseModel
# ...


base_ormar_config = ormar.OrmarConfig(
    metadata=sqlalchemy.MetaData(),
    database=databases.Database(DATABASE_URL),
)


class PydanticTest(BaseModel):
    aa: str
    bb: int


class ModelTest3(ormar.Model):
    ormar_config = base_ormar_config.copy()

    # provide your custom init function
    def __init__(self, **kwargs):
        # add value for required field without default value
        kwargs["pydantic_test"] = PydanticTest(aa="random", bb=42)
        # remember to call ormar.Model init!
        super().__init__(**kwargs)

    id: int = ormar.Integer(primary_key=True)
    name: str = ormar.String(max_length=200)
    pydantic_test: PydanticTest

test = ModelTest3(name="Test3")
assert test.name == "Test3"
assert test.pydantic_test.bb == 42
test.pydantic.aa = "new value"
assert test.pydantic.aa == "new value"

await test.save()
test_check = await ModelTest3.objects.get()

assert test_check.name == "Test3"
# after load it's back to value provided in init
assert test_check.pydantic_test.aa == "random"

!!!warning If you do not provide a value in one of the above ways ValidationError will be raised on load from database.