dataclass-factory 0.8

An utility class for creating instances of dataclasses

dataclass_factory

Why

You can convert dataclass to dict using asdict method, but cannot convert back. This module provides parse method for such task.

It is very useful in combination with json

What's supported

• dataclass from dict
• Enum from value
• List, Set, FrozenSet, Dict with specified type
• Tuple with specified types or ellipsis
• Optional with specified type
• Union parsed in order of given types
• Any returned as is
• other classes based on their __init__ method
• int/float/decimal also parsed from string
• custom parser if specified

Usage

Install:

pip install dataclass_factory 

Code:

@dataclass
class Book:
    title: str
    author: str = "Unknown author"


data = {
    "title": "Fahrenheit 451"
}

obj = dataclass_factory.parse(data, Book)  # Same as Book(title="Fahrenheit 451")

More complex example

@dataclass 
class Disk:
    title: str
    artist: str
    
    
@dataclass
class Store:
    items: List[Union[Disk, Book]]
     


data = {
    "items": [
        {"title": "Fahrenheit 451", "author": "Bradbury"},
        {"title": "Dark Side of the Moon", "artist": "Pink Floyd"}
    ]
}

expected = Store(
    items=[
        Book(title='Fahrenheit 451', author='Bradbury'),
        Disk(title='Dark Side of the Moon', artist='Pink Floyd')
    ]
)

assert expected == dataclass_factory.parse(data, Store)

Custom parsers and dict factory

You can provide your parsers for types that are not supported. For example, you can parse datetime from iso format.

Also there is dict_factory, which can help you to serialize data in your dataclasses. You can provide custom serializers as well

from dataclass_factory import parse, dict_factory
from datetime import datetime
import dateutil.parser
from dataclasses import dataclass, asdict


@dataclass
class Todo:
    id_: int
    title: str
    deadline: datetime


data = {
    "id": 1,
    "deadline": "2025-12-31T00:00:00",
    "title": "Release 1.0"
}

todo = Todo(
    id_=1,
    title="Release 1.0",
    deadline=datetime(2025, 12, 31, 0, 0, 0)
)

assert todo == parse(
    data,
    Todo,
    trim_trailing_underscore=True,
    type_factories={datetime: dateutil.parser.parse}
)

assert data == asdict(
    todo,
    dict_factory=dict_factory(
        trim_trailing_underscore=True,
        type_serializers={datetime: datetime.isoformat}
    )
)