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Description:

cattrsextras 0.2.0

cattrs-extras
This package contains advanced converter classes for cattrs, a great serialization library built around attrs.
Key features

Support for additional types: Decimal, bool, datetime, date, timedelta
Alternative structuring algorithm capable of handling complex Unions without registering additional hooks
Human-readable exceptions on structuring failure
Support for Tortoise ORM models serialization (including relations)
Additional class and Tortoise field for reversed enumerations (serialized to member name instead of value)

Installation
DEV=0 PYTHON=python make install # remove PYTHON to use pyenv
make build

Usage
from enum import Enum
from decimal import Decimal
from datetime import datetime
from attr import dataclass
from cattrs_extras.converter import Converter

class Color(Enum):
RED = 'RED'
GREEN = 'GREEN'

@dataclass(kw_only=True)
class Apple:
weight: Decimal
color: Color
best_before: datetime
sweet: bool

converter = Converter()
raw_apple = {
'weight': '200.5',
'color': 'RED',
'best_before': '2020-04-02T12:00:00',
'sweet': 'true'
}

apple = converter.structure(raw_apple, Apple)
assert apple == Apple(weight=Decimal('200.5'), color=Color.RED, best_before=datetime(2020, 4, 2, 12, 0), sweet=True)

raw_apple = converter.unstructure(apple)
assert raw_apple == {'weight': '200.5', 'color': 'RED', 'best_before': 1585818000.0, 'sweet': True}

Tortoise ORM
Important note: Tortoise ORM have chosen pydantic as a serialization library so better to stick with it. However pydantic support is still WIP, you can check current status here.
from cattrs_extras.tortoise.converter import TortoiseConverter
from cattrs_extras.tortoise.model import Model
from tortoise import fields

# TODO: ReversedCharEnumField example
class AppleModel(Model):
id = fields.IntField(pk=True)
weight = fields.DecimalField(20, 10)
color = fields.CharEnumField(Color)
best_before = fields.DateField()
sweet = fields.BooleanField()

# NOTE: Replace with module name of your models
tortoise_converter = TortoiseConverter('cattrs_extras.tortoise.model')

apple_model = tortoise_converter.structure(raw_apple, AppleModel)
assert apple_model == AppleModel(weight=Decimal('200.5'), color=Color.RED, best_before=datetime(2020, 4, 2, 12, 0), sweet=True)

raw_apple = tortoise_converter.unstructure(apple_model)
assert raw_apple == {'id': None, 'weight': '200.5', 'color': 'RED', 'best_before': 1585774800.0, 'sweet': True}

Limitations

PEP 563 – Postponed Evaluation of Annotations is not supported at the moment. Attempt to import __future__.annotations in module containing models will lead to exception. However you can still use strings as typehints.
Backward relations in Tortoise models are ignored during structuring even if fetched. Not sure if we should fix it.