Dataclass serialization / deserialization in Python

dataclasses_utils.py

import dataclasses
import importlib
import json
from typing import Any


def dataclass_from_dict(d: dict):
    try:
        modulepath, classname = d.pop("__class__").rsplit(".", 1)
        module = importlib.import_module(modulepath)
        Class = getattr(module, classname)
        return Class(**d)
    except:
        return d


class DataclassEncoder(json.encoder.JSONEncoder):
    def default(self, o: Any):
        if dataclasses.is_dataclass(o):
            d = {f.name: getattr(o, f.name) for f in dataclasses.fields(o)}
            d["__class__"] = o.__class__.__module__ + "." + o.__class__.__name__
            return d
        return o


class DataclassDecoder(json.decoder.JSONDecoder):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, object_hook=dataclass_from_dict, **kwargs)

main.py

from dataclasses_utils import 

@dataclasses.dataclass
class Contact:
    email: str
    address: str


@dataclasses.dataclass
class Account:
    username: str
    contact: str


if __name__ == "__main__":
  # create and display an account dataclass
  account = Account(
    username="toto",
    contact=Contact(email="[email protected]", address="123 Main Street, New York, NY 10030"),
  )
  print(">>>", account)

  # compute and display dataclass dump
  account_data = json.dumps(account, indent=4, cls=DataclassEncoder)
  print(account_data)

  # compute and display loaded json, with dataclass automatically deserialized into proper Python object
  print(json.loads(account_data, cls=DataclassDecoder))

output.py

# This is the output you can expect when running `python main.py`
>>> Account(username='toto', contact=Contact(email='[email protected]', address='123 Main Street, New York, NY 10030'))
>>> {
    "username": "toto",
    "contact": {
        "email": "[email protected]",
        "address": "123 Main Street, New York, NY 10030",
        "__class__": "__main__.Contact"
    },
    "__class__": "__main__.Account"
}
>>> Account(username='toto', contact=Contact(email='[email protected]', address='123 Main Street, New York, NY 10030'))