Project Links

Meta

Author: Koudai Aono

Requires Python: >=3.10

Classifiers

Development Status

4 - Beta

License

OSI Approved :: MIT License

Natural Language

English

Programming Language

Python :: 3 :: Only
Python :: 3.10
Python :: 3.11
Python :: 3.12
Python :: 3.13
Python :: 3.14
Python :: Implementation :: CPython

datamodel-code-generator

🚀 Generate Python data models from schema definitions in seconds.

📚 Documentation · 🧪 Playground · 💼 Lead maintainer available for work

[!NOTE] Playground privacy: Generation runs locally in your browser with Pyodide. Your schema and options are not sent to a backend. Shared repro URLs encode them in the URL fragment (#state=...), which browsers do not send to the server; the full URL can still be stored in your browser history or wherever you share it.

license

✨ What it does

Schema files, raw data, and existing Python models flow through datamodel-code-generator into Python model output types

Pick any one of the supported inputs and pick the Python model style you want as output. --input-model path/to/file.py:ClassName can even retarget an existing Pydantic, dataclass, or TypedDict class defined in another Python file to a different output type.

📄 Converts OpenAPI 3, AsyncAPI, JSON Schema, Apache Avro, XML Schema, Protocol Buffers/gRPC, GraphQL, MCP tool schemas, and raw data (JSON/YAML/CSV) into Python models
🐍 Generates from existing Python types (Pydantic, dataclass, TypedDict) via --input-model
🎯 Generates Pydantic v2, Pydantic v2 dataclass, dataclasses, TypedDict, or msgspec output
🔗 Handles complex schemas: $ref, allOf, oneOf, anyOf, enums, and nested types
✅ Produces type-safe, validated code ready for your IDE and type checker

📦 Installation

Recommended for standalone CLI use:

uv tool install datamodel-code-generator

Conda users can install from conda-forge:

conda install -c conda-forge datamodel-code-generator

For projects that should pin the generator version, add it as a development dependency instead:

uv add --dev datamodel-code-generator

[!NOTE] Community-maintained distribution packages are also available from Debian, Ubuntu, nixpkgs, and openSUSE Tumbleweed. Availability and versions vary by distribution.

Other installation methods

pip:

pip install datamodel-code-generator

uv (run without adding to project):

uv run --with datamodel-code-generator datamodel-codegen --help

With HTTP support (for resolving remote $ref):

pip install 'datamodel-code-generator[http]'

With GraphQL support:

pip install 'datamodel-code-generator[graphql]'

With Protocol Buffers support:

pip install 'datamodel-code-generator[protobuf]'

Docker:

docker pull koxudaxi/datamodel-code-generator

Published Docker images run as a non-root appuser. When writing generated files to a bind-mounted directory, make sure the directory is writable by the container user or pass an explicit Docker user, for example --user "$(id -u):$(id -g)".

🏃 Quick Start

Command

datamodel-codegen \
  --input schema.json \
  --input-file-type jsonschema \
  --output-model-type pydantic_v2.BaseModel \
  --preset standard-py312-20260619 \
  --output model.py

This quick start uses standard-py312-20260619 as the modern Python 3.12 baseline. Preset names include the target Python version: py312 means Python 3.12.

See CLI Reference for all options. See Presets, --preset, --input-file-type, and --output-model-type for this command.

For more schema-aware output that preserves schema-authored names, reuses models, and embeds generated documentation, use practical-py312-20260619.

Input (schema.json)

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "title": "Pet",
  "type": "object",
  "required": ["name"],
  "properties": {
    "name": {
      "type": "string",
      "description": "The pet's name"
    },
    "species": {
      "type": "string",
      "enum": ["dog", "cat", "bird", "fish"],
      "default": "dog"
    },
    "age": {
      "type": "integer",
      "minimum": 0,
      "description": "Age in years"
    },
    "vaccinated": {
      "type": "boolean",
      "default": false
    }
  }
}

Output (model.py)

# generated by datamodel-codegen:
#   filename:  schema.json

from __future__ import annotations

from enum import StrEnum
from typing import Annotated

from pydantic import BaseModel, ConfigDict, Field


class Species(StrEnum):
    dog = 'dog'
    cat = 'cat'
    bird = 'bird'
    fish = 'fish'


class Pet(BaseModel):
    model_config = ConfigDict(
        populate_by_name=True,
    )
    name: Annotated[str, Field(description="The pet's name")]
    species: Species = Species.dog
    age: Annotated[int | None, Field(description='Age in years', ge=0)] = None
    vaccinated: bool = False

⚡ Speed up generation

By default, generated Python is currently formatted with black and isort. For faster generation without external formatter dependencies, add --formatters builtin for standard generated model modules. In a future version, the Black/isort dependencies will become opt-in and the default formatter will change to builtin.

If you prefer Ruff, install it with pip install 'datamodel-code-generator[ruff]' and use --formatters ruff-check ruff-format for a fast external formatter.

Custom templates can emit Python outside the standard generated model patterns covered by builtin, so custom-template output is not exhaustively validated. If --formatters builtin produces invalid or poorly formatted output with a custom template, please open an issue with a small reproducer. See Formatter Behavior for details.

See Performance Benchmarks for release benchmark data and interactive charts.

📖 Documentation

👉 Read the full documentation →

🧰 Presets - Recommended option bundles for modern output
🚀 Getting Started - Installation and first model
🖥️ CLI Reference - All command-line options
🧪 Playground - Try generation in your browser
⚙️ pyproject.toml - Configuration file
🔄 CI/CD Integration - GitHub Actions, pre-commit hooks
✅ Conformance Dashboard - External corpus coverage signals
📈 Performance Benchmarks - Release benchmark tables and interactive charts
🧭 Architecture - Generation pipeline and synchronized component inventory
🚀 One-liner Usage - uvx, pipx, clipboard integration
❓ FAQ - Common questions

📥 Supported Input

OpenAPI 3 (YAML/JSON)
AsyncAPI (YAML/JSON)
JSON Schema
MCP tool schemas
XML Schema (XSD)
Protocol Buffers / gRPC (.proto)
Apache Avro schema (AVSC)
JSON data
YAML data
Python dictionary
CSV data
GraphQL schema
Python types (Pydantic, dataclass, TypedDict) via --input-model

📤 Supported Output

pydantic v2 BaseModel
pydantic v2 dataclass
dataclasses
TypedDict
msgspec Struct

✅ Conformance Signals

CI exercises datamodel-code-generator against pinned external corpora for XML Schema, JSON Schema, AsyncAPI, Apache Avro, and Protocol Buffers. See the Conformance Dashboard for the generated summary of runner scripts, tox environments, CI jobs, expected corpus counts, and upstream sources.

🍳 Common Recipes

CLI option quick starts

Use these starting points when combining options; each option links to the generated CLI reference for details and examples.

Generate a local schema file: Pin the input type and destination when the source extension is ambiguous or generated output needs a stable path. Options: --input, --input-file-type, --output.
Target Pydantic v2 on modern Python: Set the output model family and Python/Pydantic compatibility targets together. Options: --output-model-type, --target-python-version, --target-pydantic-version.
Use modern Python annotations: Target a recent Python version and prefer built-in collection and union syntax in generated types. Options: --target-python-version, --use-union-operator, --use-standard-collections.
Normalize incoming field names: Convert source names to Python identifiers while preserving explicit alias data for runtime IO. Options: --snake-case-field, --original-field-name-delimiter, --aliases.
Generate operation-focused models: Limit OpenAPI output to operation shapes and name models from operation IDs and status codes. Options: --openapi-scopes, --use-operation-id-as-name, --use-status-code-in-response-name.
Resolve remote references deliberately: Enable remote $ref loading and configure request metadata, timeouts, or local ref roots. Options: --allow-remote-refs, --http-headers, --http-timeout, --http-local-ref-path.

See the CLI Reference for the full option list and category-specific recipes.

🤖 Get CLI Help from LLMs

Generate a prompt to ask LLMs about CLI options:

datamodel-codegen --generate-prompt "Best options for Pydantic v2?" | claude -p

See LLM Integration for more examples.

🌐 Generate from URL

pip install 'datamodel-code-generator[http]'
datamodel-codegen --url https://example.com/api/openapi.yaml --output model.py

⚙️ Use with pyproject.toml

[tool.datamodel-codegen]
input = "schema.yaml"
output = "src/models.py"
output-model-type = "pydantic_v2.BaseModel"

Then simply run:

datamodel-codegen

See pyproject.toml Configuration for more options.

🔄 CI/CD Integration

Validate generated models in your CI pipeline:

# Replace vX.Y.Z with a released action version.
- uses: koxudaxi/datamodel-code-generator@vX.Y.Z
  with:
    input: schemas/api.yaml
    output: src/models/api.py

See CI/CD Integration for more options.

Coding agent skill

This repository includes an experimental Agent Skill that teaches compatible coding agents to run datamodel-codegen when generating Python models from OpenAPI, AsyncAPI, JSON Schema, GraphQL, JSON/YAML/CSV sample data, MCP tool schemas, Protocol Buffers, XML Schema, Apache Avro, or existing Python model objects.

See Coding Agent Skill for detailed guidance and troubleshooting.

Install the directory for your agent:

# Codex, project-local
mkdir -p .agents/skills
cp -R skills/datamodel-code-generator .agents/skills/datamodel-code-generator

# Claude Code, project-local
mkdir -p .claude/skills
cp -R skills/datamodel-code-generator .claude/skills/datamodel-code-generator

For a personal install, copy the same directory to $HOME/.agents/skills/datamodel-code-generator/ for Codex or ~/.claude/skills/datamodel-code-generator/ for Claude Code.

Check your agent's current documentation for exact search paths.