dataclasses-json 0.0.13

Easily serialize dataclasses to and from JSON

Dataclasses JSON

This library provides a simple API for encoding and decoding dataclasses to and from JSON.

It's recursive (see caveats below), so you can easily work with nested dataclasses.

In addition to the supported types in the py to JSON table, any arbitrary Collection type is supported (they are encoded into JSON arrays, but decoded into the original collection types).

The latest release is compatible with both Python 3.7 and Python 3.6 (with the dataclasses backport).

Quickstart

pip install dataclasses-json

Approach 1: Class decorator

from dataclasses import dataclass
from dataclasses_json import dataclass_json

@dataclass_json
@dataclass
class Person:
    name: str

lidatong = Person('lidatong')

# Encoding to JSON
encoded_lidatong = lidatong.to_json()
assert encoded_lidatong == '{"name": "lidatong"}'

# Decoding from JSON
decoded_lidatong = Person.from_json('{"name": "lidatong"}')
assert decoded_lidatong == lidatong

Note that the @dataclass_json decorator must be stacked above the @dataclass decorator (order matters!)

Approach 2: Inherit from a mixin

from dataclasses import dataclass
from dataclasses_json import DataClassJsonMixin

@dataclass
class Person(DataClassJsonMixin):
    name: str

lidatong = Person('lidatong')
assert Person.from_json(lidatong.to_json()) == lidatong

Pick whichever approach suits your taste. The differences in implementation are invisible in usage.

A larger example

from dataclasses import dataclass
from dataclasses_json import DataClassJsonMixin
from typing import List


@dataclass(frozen=True)
class Minion(DataClassJsonMixin):
    name: str


@dataclass(frozen=True)
class Boss(DataClassJsonMixin):
    minions: List[Minion]

boss = Boss([Minion('evil minion'), Minion('very evil minion')])
boss_json = """
{
    "minions": [
        {
            "name": "evil minion"
        },
        {
            "name": "very evil minion"
        }
    ]
}
""".strip()

assert boss.to_json(indent=4) == boss_json
assert Boss.from_json(boss_json) == boss

Caveats

Data Classes that contain forward references (e.g. recursive dataclasses) are not currently supported.