JSON to Python Dataclass

Generate Python dataclasses from JSON instantly. Supports @dataclass, Pydantic v2 BaseModel, and TypedDict. Handles nested objects, arrays, optional fields, and custom root class names. Free, runs in your browser.

100% Client-Side Your data never leaves your browser Free · No Sign-Up
Mode
JSON Input
Python Output

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How to Use

  1. Paste or type your JSON into the left panel. The tool validates it in real time.
  2. Optionally set a Root class name (default: Root).
  3. Choose an output mode: @dataclass, Pydantic v2, or TypedDict.
  4. Click Generate Python or wait for real-time conversion.
  5. Click Copy to copy the output, or Download .py to save as a file.

Type Mapping

  • null → Optional[Any] = None
  • string → str
  • integer → int
  • float → float
  • boolean → bool
  • array → List[T]
  • mixed array → List[Union[T1, T2]]
  • nested object → separate class

Example

Given this JSON:

{"user": {"first_name": "Alice", "age": 30}, "tags": ["admin"], "note": null}

The tool generates (@dataclass mode):

from dataclasses import dataclass
from typing import Any, List, Optional

@dataclass
class User:
    first_name: str
    age: int

@dataclass
class Root:
    user: User
    tags: List[str]
    note: Optional[Any] = None

FAQ

What does this tool generate?

It generates Python class definitions from JSON. Choose between standard @dataclass (stdlib), Pydantic v2 BaseModel, or TypedDict. Each nested object becomes its own named class.

What output modes are supported?

Three modes: @dataclass (Python stdlib, default), Pydantic v2 BaseModel, and TypedDict (Python 3.8+).

How are JSON types mapped to Python types?

string → str, integer → int, float → float, boolean → bool, null → Optional[Any], array → List[T], nested object → separate class.

When are fields marked as Optional?

A field is marked Optional[T] = None when its value is null in the JSON sample, or when it is missing in some objects of a merged array.

How are nested objects handled?

Each nested object is extracted into a separate class named after the field key in PascalCase. Child classes are always defined before the parent class so the output is immediately usable.

Is my data sent to a server?

No. The entire conversion runs in your browser. No data leaves your machine.