Custom Encoders (JSONEncoder)

Extend JSONEncoder to handle custom Python objects that aren't JSON serializable by default.

Creating Custom Encoders

Subclass JSONEncoder to handle custom types.

import json
from datetime import datetime

class DateTimeEncoder(json.JSONEncoder):
    def default(self, obj):
        if isinstance(obj, datetime):
            return obj.isoformat()
        return super().default(obj)

data = {
    "event": "Conference",
    "date": datetime(2024, 12, 25, 14, 30)
}

json_str = json.dumps(data, cls=DateTimeEncoder)
print(json_str)

{"event": "Conference", "date": "2024-12-25T14:30:00"}

Using default Parameter

Use the default parameter for simpler custom encoding.

import json
from datetime import date

def encode_date(obj):
    if isinstance(obj, date):
        return obj.isoformat()
    raise TypeError(f"Object of type {type(obj)} is not JSON serializable")

data = {
    "name": "Alice",
    "birth_date": date(1990, 5, 15)
}

json_str = json.dumps(data, default=encode_date)
print(json_str)

{"name": "Alice", "birth_date": "1990-05-15"}