dataclass-as-data 0.1.0

Simple configurable conversion of dataclasses to raw data

Dataclass As Data

This is a simple package for configurable conversion of dataclasses to a data representation, typically a dict or a tuple. The behaviour for how a dataclass is converted to and from data can be configured to differ from the default per dataclass if desired.

This package only supports simple primitive types, other dataclasses, and the primitive generics dict[...], list[...], tuple[...], Union[...], and Optional[...] as type annotations by default. Single-Input functions can be used in the place of type hints as simple converters.

Install

This package supports Python 3.9 and above.

pip install dataclass-as-data

Quick Start

import dataclasses
from dataclass_as_data import as_data, from_data


# Create a dataclass
@dataclasses.dataclass
class Person:
    name: str
    age: int

    
# Create a dataclass object
person = Person("Simon", 21)

>>> person
Person(name='Simon', age=21)

# Call as_data with the dataclass object to convert it to a dictionary
data = as_data(person)

>>> data
{'name': 'Simon', 'age': 21}

# Call from_data with the dataclass and the data to get the object instance back
>>> from_data(Person, data)
Person(name='Simon', age=21)

Dataclasses can be nested within dataclasses, which are recursively converted to their data representation.

@dataclasses.dataclass
class Friends:
    people: list[Person]


# All dataclasses are converted recursively
>>> as_data(Friends([Person("Sunset", 22), Person("Starlight", 20)]))
{'people': [{'name': 'Sunset', 'age': 22}, {'name': 'Starlight', 'age': 20}]}

>>> from_data(Friends, {'people': [{'name': 'Sunset', 'age': 22}, {'name': 'Starlight', 'age': 20}]})
Friends(people=[Person(name='Sunset', age=22), Person(name='Starlight', age=20)])

Configuring as_data and from_data

To change what data is constructed when using as_data and from_data, override the as_data method and from_data class methods in your dataclass.

Note: you must use one of as_dict, as_tuple, from_dict, or from_tuple (not as_data or from_data) if you wish to use the default behaviour and modify it.

from dataclass_as_data import as_data, as_dict, from_data, from_dict


@dataclasses.dataclass
class Config:
    VERSION = (1, 0)
    version: tuple[int, int] = VERSION
    
    def as_data(self) -> dict:
        # Ensure correct version when converting to data
        assert self.version == self.VERSION, "Incorrect version!"
        
        return as_dict(self)  # use as_dict to otherwise use default behaviour
    
    @classmethod
    def from_data(cls, data: dict):
       # Update version on data load
        if data['version'] < cls.VERSION:
            data['version'] = cls.VERSION

        return from_dict(cls, data)  # use from_dict to otherwise use default behaviour


# Now these methods are called instead
>>> as_data(Config((0, 1)))
AssertionError: Incorrect version!

>> from_data(Config, {'version': (0, 1)})
Config(version=(1, 0))

DataAsTuple

If you'd simply like a dataclass to be represented as a tuple instead of a dict when calling as_data, inherent from the DataAsTuple abstract base class.

from dataclass_as_data import as_data, DataAsTuple


# Create a dataclass inheriting from DataAsTuple
@dataclasses.dataclass
class Person(DataAsTuple):
    name: str
    age: int

    
# Calling as_data now returns a tuple
>>> as_data(Person("Summer", 24))
("Summer", 24)

This merely overrides as_data and from_data to use as_tuple and from_tuple for you respectively.

from dataclass_as_data import as_tuple, from_tuple


# Same as inheriting from DataAsTuple
@dataclasses.dataclass
class Person:
    name: str
    age: int
    
    def as_data(self):
        return as_tuple(self)

    @classmethod
    def from_data(cls, data: tuple):
        return from_tuple(cls, data)

Custom converters

from_data supports very basic custom converters in the form on single-input functions. These converters are called on the relevant data entries when from_data is called. Note that regular types, such as int, are also technically treated this way.

Note: as_data performs no type conversion at all.

from dataclass_as_data import from_data


def lower_str(value) -> str:
    """Convert to lowercase str"""
    return str(value).lower()

    
@dataclasses.dataclass
class Employee:
    id: int
    name: lower_str


# The `lower_str` converter is called on the value of the `name` parameter
>>> from_data(Employee, {'id': 123, 'name': "Sylvester"})
Employee(id=123, name='silvia')

# The string value of `id` is coerced into an int
>>> from_data(Employee, {'id': "456", 'name': "Sunny"})
Employee(id=456, name='sunny')