import json

class B:
    def __init__(self):
        self.value = 10

b = B()
print(json.dumps(b.__dict__))

import json

data = {"user": {"id": 123, "active": True}}
with open("data.json", "w") as f:
    json.dump(data, f)

with open("data.json", "r") as f:
    loaded = json.load(f)

print(loaded["user"]["id"])

import json

data = {"users": [{"name": "Alice"}, {"name": "Bob"}]}
print(json.dumps(data, indent=2))

import json
from datetime import date

today = date(2025, 6, 9)

def handle(obj):
    if isinstance(obj, date):
        return obj.isoformat()
    raise TypeError("Not serializable")

print(json.dumps({"today": today}, default=handle))