Python dataclass serialization to/from JSON

Need to convert dataclasses to JSON and back, handling nested objects, dates, and enums.

Multiple approaches for dataclass serialization:

from dataclasses import dataclass, asdict, field
from datetime import datetime
from enum import Enum
import json

class Status(Enum):
    ACTIVE = 'active'
    INACTIVE = 'inactive'

@dataclass
class User:
    name: str
    email: str
    status: Status = Status.ACTIVE
    created_at: datetime = field(default_factory=datetime.now)
    tags: list[str] = field(default_factory=list)

# Method 1: Custom encoder
class DataclassEncoder(json.JSONEncoder):
    def default(self, o):
        if hasattr(o, '__dataclass_fields__'):
            return asdict(o)
        if isinstance(o, datetime):
            return o.isoformat()
        if isinstance(o, Enum):
            return o.value
        return super().default(o)

user = User('Alice', 'alice@example.com')
json_str = json.dumps(user, cls=DataclassEncoder, indent=2)

# Method 2: dacite for deserialization
from dacite import from_dict, Config

data = json.loads(json_str)
user = from_dict(User, data, config=Config(
    type_hooks={datetime: datetime.fromisoformat}
))

# Method 3: Pydantic (most robust)
from pydantic import BaseModel

class UserModel(BaseModel):
    name: str
    email: str
    status: Status = Status.ACTIVE
    created_at: datetime = field(default_factory=datetime.now)
    tags: list[str] = []

user = UserModel(name='Alice', email='alice@example.com')
json_str = user.model_dump_json()
user = UserModel.model_validate_json(json_str)

Dataclasses don't include serialization by default. asdict() handles basic cases but not dates, enums, or deserialization.

Python APIs and data processing needing JSON serialization