CuratedPython 3.12local

TypeError: Object of type X is not JSON serializable

Problem

`json.dumps(obj)` fails because the object (datetime, Decimal, set, numpy type, dataclass, etc.) isn't a built-in JSON type.

Solution

python

Convert to a JSON-friendly form first: `datetime` to `.isoformat()`, `Decimal` to `float`/`str`, `set` to `list`, a dataclass via `dataclasses.asdict()`. Or pass a `default` hook: `json.dumps(obj, default=str)` for a quick fix, or a custom `JSONEncoder` for precise control.