pyldraw3

A modern Python package for creating and manipulating LDraw format files - the standard for CAD applications that create LEGO models. It is a drop-in replacement for the unmaintained pyldraw library.

Features

• 🧱 Complete LDraw Support: Full compatibility with the LDraw standard format
• 🐍 Pythonic API: Import LEGO parts directly as Python modules
• 📦 Dynamic Library Generation: Automatically generate Python modules from LDraw libraries
• 📜 Comprehensive Guide: Jump into example or the quick start below, or read a detailed usage guide

Table of Contents

• Features
• Quick Start
  • Installation
  • Setup
  • Examples
  • Basic Usage
• Requirements
• Configuration
• CLI Reference
• Development
  • Setup Development Environment
  • Development Commands
• Architecture
  • Core Components
  • Key Classes
• Contributing
• License
• Trademarks
• Credits

Quick Start

Installation

uv add pyldraw3

Setup

Activate your virtual environment and set up the LDraw library - this will download the LDraw library and create the parts classes:

source .venv/bin/activate
ldraw download --yes
ldraw generate --yes

By default ldraw download fetches the complete LDraw release (~80 MB, everything LDraw publishes). To pin a specific dated release instead - useful for reproducible builds or a smaller download - pass --version, e.g. ldraw download --version 2018-02 --yes. Each downloaded release is cached separately, and ldraw generate builds ldraw.library.* from whichever release is currently configured (see Configuration).

Examples

Check the examples/ directory for sample scripts demonstrating various features:

# Run an example
python examples/figures.py > my_model.ldr

Basic Usage

This package allows users to create LDraw scene descriptions using Pieces which are Parts that have a specific position and orientation. Piece.to_ldraw() and Group.to_ldraw() produce LDraw file content; str(piece) and str(group) delegate to those serializers:

from ldraw.library.colours import Light_Grey
from ldraw.library.parts.bricks import Brick1X2WithClassicSpaceLogoPattern
from ldraw.pieces import Group, Piece
from ldraw.geometry import Vector, Identity

# Create a simple model
model = Group()
Piece(Light_Grey, Vector(-10, -32, -90), Identity(), Brick1X2WithClassicSpaceLogoPattern, model)

with open("my_model.ldr", "w") as ldr_file:
    print(model, file=ldr_file)

ldraw.library.* is generated by ldraw generate and gives you every part as an importable, autocompletable Python name (as used above). If you'd rather look a part up by its catalog description or LDraw code at runtime - for example when the part name isn't known until your program runs - load the parts catalog directly instead:

from pathlib import Path

from ldraw.config import Config
from ldraw.parts import Parts

config = Config.load()
parts = Parts(Path(config.ldraw_library_path) / "ldraw" / "parts.lst")
cowboy_hat = parts.get_entry_by_description("Hat Cowboy").code  # -> "3629"
head = parts.get_entry_by_description("Head with Solid Stud").code  # -> "3626a"
brick1x1 = parts.get_entry_by_description("Brick  1 x  1").code  # -> "3005"

Both cowboy_hat and Brick1X2WithClassicSpaceLogoPattern are just LDraw part code strings, so either style can be passed as the part argument to Piece.

Requirements

• Python 3.12+

Configuration

ldraw download and ldraw generate write their settings to a YAML config file in an OS-appropriate config directory (via platformdirs). Run ldraw config to see the current values:

$ ldraw config
generated_path: /Users/you/Library/Application Support/pyldraw3/generated
ldraw_library_path: /Users/you/Library/Caches/pyldraw3/2018-02

• ldraw_library_path - the downloaded LDraw release currently in use (switch releases by re-running ldraw download --version ...)
• generated_path - where ldraw generate writes the ldraw.library.* package that you import

CLI Reference

usage: ldraw [-h] command ...

Download the LDraw parts library and generate the ldraw.library Python
modules.

positional arguments:
  command
    download  Download and unpack an LDraw parts library release.
    generate  Generate the ldraw.library modules from the downloaded library.
    config    Print the current configuration.
    version   Print the installed pyldraw3 version.

options:
  -h, --help  show this help message and exit

• ldraw download [--version VERSION] [--yes] - download and unpack an LDraw release (default version: complete)
• ldraw generate [--yes] [--force] - (re)generate ldraw.library.* from the currently configured release; --force regenerates even if already up to date
• ldraw config - print the current configuration as YAML
• ldraw version - print the installed pyldraw3 version

Run ldraw <command> --help for a command's full option list.

Development

This project uses uv for dependency management and packaging.

Setup Development Environment

# Clone the repository
git clone https://github.com/hbmartin/pyldraw3.git
cd pyldraw3

# Install dependencies
uv sync

# Activate virtual environment
source .venv/bin/activate

# Download and set up LDraw library
uv run ldraw download --version 2018-02 --yes
uv run ldraw generate --yes

Development Commands

# Run tests
uv run pytest                 # All tests
uv run pytest --cov=ldraw     # With coverage
uv run pytest --integration   # Integration tests only

# Code formatting and linting
uv run black .               # Format code
uv run ruff check            # Lint code
uv run ruff check --fix      # Fix linting issues

# Build package
uv build

Architecture

Core Components

• CLI Interface (ldraw/cli.py): Command-line interface with download, generate, config, and version subcommands
• Dynamic Library Generation (ldraw/generation/): Converts LDraw libraries to Python modules
• Import System (ldraw/imports.py): Custom meta path hook for dynamic imports

Key Classes

• Parts - Manages parts catalog and loading
• Piece - Represents individual LEGO pieces in models
• Figure - High-level minifigure construction
• Geometry classes - Matrix operations and 3D mathematics

Contributing

Contributions are welcome! See CONTRIBUTING.md for the fork/branch/PR workflow.

License

This project is licensed under the GNU General Public License v3.0 or later - see the license (COPYING) file for details.

pyldraw, a Python package for creating LDraw format files.
Copyright (C) 2008 David Boddie <david@boddie.org.uk>
Some parts Copyright (C) 2021 Matthieu Berthomé <matthieu@mmea.fr>
Some parts Copyright (C) 2025 Harold Martin <harold.martin@gmail.com>

Trademarks

LDraw is a trademark of the Estate of James Jessiman. LEGO is a registered trademark of the LEGO Group.

Credits

• Original Author: David Boddie
• Previous Maintainer: Matthieu Berthomé
• Current Maintainer: Harold Martin

This repository was extracted from the original Mercurial repository and modernized for current Python practices.