4 JsonSerializableMixin Patterns in Python for Cleaner Serialization

[TIPS] Python Mixins - JsonSerializableMixin

1. Basic JsonSerializableMixin

Quickly dumps all attributes into JSON

import json

class JsonSerializableMixin:

    def to_json(self):

        return json.dumps(vars(self))



class Product(JsonSerializableMixin):

    def __init__(self, name, price):

        self.name = name

        self.price = price



print(Product("Laptop", 1200).to_json())

# {"name": "Laptop", "price": 1200}

=> Fast and simple

BUT: Doesn’t handle nested objects or special types.

2. Custom Field Whitelist

Only include specific fields (__json_fields__)

import json



class JsonWhitelistMixin:

    __json_fields__ = []



    def to_json(self):

        data = {field: getattr(self, field) for field in self.__json_fields__ if hasattr(self, field)}

        return json.dumps(data)





class User(JsonWhitelistMixin):

    __json_fields__ = ["username", "email"]



    def __init__(self, username, email, password):

        self.username = username

        self.email = email

        self.password = password  # excluded





print(User("Joe", "[email protected]", "amazing Python team").to_json())

# {"username": "Joe", "email": "[email protected]"}

=> Great for security (hide passwords, tokens, etc.).

3. Nested Object Support

Handles lists, dicts, and other objects with to_json() or to_dict()

import json



class JsonNestedMixin:

    def to_dict(self):

        def convert(obj):

            if isinstance(obj, list):

                return [convert(i) for i in obj]

            if isinstance(obj, dict):

                return {k: convert(v) for k, v in obj.items()}

            if hasattr(obj, "to_dict"):

                return obj.to_dict()

            return obj



        return {k: convert(v) for k, v in vars(self).items()}



    def to_json(self):

        return json.dumps(self.to_dict())





class Address(JsonNestedMixin):

    def __init__(self, city, country):

        self.city = city

        self.country = country





class Person(JsonNestedMixin):

    def __init__(self, name, addresses):

        self.name = name

        self.addresses = addresses





p = Person("Glinteco", [Address("Hanoi", "Vietnam"), Address("Melbourne", "Australia")])

print(p.to_json())

# {"name": "Glinteco", "addresses": [{"city": "Hanoi", "country": "Vietnam"}, {"city": "Melbourne", "country": "Australia"}]}

=> Handles real-world object graphs.

4. Custom Encoder for Non-JSON Types

Supports datetime, Decimal, or other special types

import json, datetime, decimal





class CustomEncoder(json.JSONEncoder):

    def default(self, obj):

        if isinstance(obj, datetime.datetime):

            return obj.isoformat()

        if isinstance(obj, decimal.Decimal):

            return float(obj)

        return super().default(obj)





class JsonCustomEncoderMixin:

    def to_json(self):

        return json.dumps(vars(self), cls=CustomEncoder)





class Invoice(JsonCustomEncoderMixin):

    def __init__(self, amount, issued_at):

        self.amount = decimal.Decimal(amount)

        self.issued_at = issued_at





print(Invoice("1200.50", datetime.datetime(2025, 9, 6, 14, 30)).to_json())

# {"amount": 1200.5, "issued_at": "2025-09-06T14:30:00"}