Local-first Python type generation
Python dataclass and Pydantic model generation occurs strictly in your browser's local memory. Your production JSON payloads never touch a remote server.
Python Dataclasses from JSON
Python 3.7 introduced dataclasses, and they've become the standard way to represent structured data. No more writing __init__, __repr__, and __eq__methods by hand. But you still need to define the fields and their types. This tool does that part for you.
Paste your JSON, and you get properly annotated Python dataclasses with the right types —str, int, float, bool, List[T], and nested class references. The imports are included at the top. Copy, paste into your project, and you've got typed data structures ready for mypy and IDE autocompletion.
Why Dataclasses Over Plain Dicts
You could just use json.loads() and work with dictionaries, but you lose all the benefits of typed code. No autocomplete, no type checking, no protection against typos in key names. With dataclasses, your editor knows exactly what fields exist and what types they are. It catches bugs before you run the code.
FastAPI and Pydantic
If you're building APIs with FastAPI, you'll want Pydantic models instead of dataclasses. The structure is almost identical — rename @dataclass to BaseModeland remove field() calls. The generated class gives you the field structure, and converting to Pydantic is a 30-second edit. You could also use our Zod converter as a TypeScript equivalent.
Working with Nested JSON
Real-world APIs return deeply nested JSON. This tool creates separate dataclass definitions for each nested object and uses forward references ("ClassName") to handle circular dependencies. Arrays of objects get properly typed as List[NestedClass]. The generated code handles the structural complexity so you can focus on using the data.
Type Hints and mypy Compatibility
The generated code uses standard Python type hints that work with mypy, pyright, and all major IDEs. We use List from typing for Python 3.7-3.8 compatibility. If you're on Python 3.9+, you can replace List[str] with list[str]directly — it's a one-line find-and-replace.
Related JSON Tools
For FastAPI projects, adapt the output to Pydantic models. Need frontend types too? Generate TypeScript interfaces from the same JSON. Validate your JSON syntax with our JSON Validator before converting.