pydantic-views 0.1.0

Views for Pydantic models

View for Pydantic models documentation

This package provides a simple way to create views from pydantic models. A view is another pydantic models with some of field of original model. So, for example, read only fields does not appears on Create or Update views.

As rest service definition you could do:

ExampleModelCreate = BuilderCreate().build_view(ExampleModel)
ExampleModelCreateResult = BuilderCreateResult().build_view(ExampleModel)
ExampleModelLoad = BuilderLoad().build_view(ExampleModel)
ExampleModelUpdate = BuilderUpdate().build_view(ExampleModel)

def create(input: ExampleModelCreate) -> ExampleModelCreateResult: ...
def load(model_id: str) -> ExampleModelLoad: ...
def update(model_id: str, input: ExampleModelUpdate) -> ExampleModelLoad: ...

Features

• Unlimited views per model.

• Create view for referenced inner models.

• It is possible to set a view manually.

• Tested code.

• Full typed.

• Opensource.

Installation

Using pip:

pip install pydantic-views

Using poetry:

poetry add pydantic-views

How to use

When you define a pydantic model you must mark the access model for each field. It means you should use our annotations to define field typing.

from typing import Annotated
from pydantic import BaseModel, gt
from pydantic_views import ReadOnly, ReadOnlyOnCreation, Hidden, AccessMode

class ExampleModel(BaseModel):

    # No marked fields are treated like ReadAndWrite fields.
    field_str: str

    # Read only fields are removed on view for create and update views.
    field_read_only_str: ReadOnly[str]

    # Read only on creation fields are removed on view for create, update and load views.
    # But it is shown on create result view.
    field_api_secret: ReadOnlyOnCreation[str]

    # It is possible to set more than one access mode and to use annotation standard pattern.
    field_int: Annotated[int, AccessMode.READ_ONLY, AccessMode.WRITE_ONLY_ON_CREATION, gt(5)]

    # Hidden field do not appears in any view.
    field_hidden_int: Hidden[int]

    # Computed fields only appears on reading views.
    @computed_field
    def field_computed_field(self) -> int:
        return self.field_hidden_int * 5

So, in order to build a Load view it is so simple:

from pydantic_views import BuilderLoad

ExampleModelLoad = BuilderLoad().build_view(ExampleModel)

It is equivalent to:

from pydantic import gt
from pydantic_views import View

class ExampleModelLoad(View[ExampleModel]):
    field_str: str
    field_int: Annotated[int, gt(5)]
    field_computed_field: int

In same way to build a Update view you must do:

from pydantic_views import BuilderUpdate

ExampleModelUpdate = BuilderUpdate().build_view(ExampleModel)

It is equivalent to:

from pydantic import PydanticUndefined
from pydantic_views import View

class ExampleModelUpdate(View[ExampleModel]):
    field_str: str = Field(default_factory=lambda: PydanticUndefined)

As you can see, on Update view all fields has a default factory returning PydanticUndefined in order to make them optionals. And when an update view is applied to a given model, the fields that are not set (use default value) will not be applied to the model.

original_model = ExampleModel(
    field_str="anything"
    field_read_only_str="anything"
    field_api_secret="anything"
    field_int=10
    field_hidden_int=33
)

update = ExampleModelUpdate(field_str="new_data")

updated_model = update.view_apply_to(original_model)

assert isinstance(updated_model, ExampleModel)
assert updated_model.field_str == "new_data"

But if a field is not set on update view, the original value is kept.

original_model = ExampleModel(
    field_str="anything"
    field_read_only_str="anything"
    field_api_secret="anything"
    field_int=10
    field_hidden_int=33
)

update = ExampleModelUpdate()

updated_model = update.view_apply_to(original_model)

assert isinstance(updated_model, ExampleModel)
assert updated_model.field_str == "anything"