pyd3js-delaunay

Python port of d3-delaunay for Delaunay triangulation and Voronoi diagrams, aligned with the other pyd3js packages.

Tracked upstream: d3-delaunay@6.0.4 — see upstream_lock.json.

Requirements: Python 3.10+.

What is d3-delaunay?

d3-delaunay builds a Delaunay triangulation from planar points and derives a Voronoi diagram (clipped to a viewport). It is the standard geometric core D3 uses for mesh and Voronoi layouts.

This package gives you the same workflow in Python: construct a Delaunay, optionally call voronoi(bounds), and use render helpers that return SVG path strings (like upstream).

What you get

• Delaunay and Voronoi matching the pinned upstream API (see compatibility matrix below).
• Pure Python tests: upstream Mocha suites are ported to pytest (no Node.js / npm gate).
• py.typed and type-checked public surface (see Development).

Quickstart (verified)

Flat coordinates match upstream new Delaunay(points):

from array import array
from pyd3js_delaunay import Delaunay

coords = array("d", [0, 0, 1, 0, 0, 1])
d = Delaunay(coords)
v = d.voronoi([0, 0, 1, 1])
print(list(d.hull), v.render_bounds())

[0, 2, 1] M0,0h1v1h-1Z

Point lists use Delaunay.from_points (same idea as JS Delaunay.from):

from pyd3js_delaunay import Delaunay

d = Delaunay.from_points([[0, 0], [1, 0], [0, 1]])
print(list(d.triangles))

[0, 2, 1]

If bounds is omitted, d.voronoi() uses the upstream default [0, 0, 960, 500].

Install

From PyPI:

pip install pyd3js-delaunay

This repo is a uv workspace. For local development:

uv sync --group dev

Dependencies

Triangulation topology (triangles, halfedges, hull) comes from dylaunator ==0.1.0 (Python port of mapbox/delaunator), which uses pyrobust-predicates for adaptive-precision orient2d — the same dependency chain as JavaScript (delaunator → robust-predicates).

Compatibility matrix

Symbols match upstream exports listed in docs/UPSTREAM_API.md.

• Delaunay — [implemented]
• Voronoi — [implemented]

The Python package also exports __version__.

JavaScript naming

Methods are snake_case in Python. Voronoi additionally exposes camelCase aliases (renderCell, renderBounds, cellPolygon, cellPolygons). Internal Path / Polygon helpers use canvas-style names (moveTo, lineTo, closePath).

No Node / npm

Runtime and tests do not require Node.js, npm, or a JavaScript oracle.

Documentation

• User guide: docs/USER_GUIDE.md
• Upstream inventory & ported tests: docs/UPSTREAM_API.md
• Changelog: docs/CHANGELOG.md
• Roadmap: docs/ROADMAP.md
• Updating the upstream pin: docs/UPSTREAM_UPDATE.md

Development

uv run pytest packages/pyd3js-delaunay/package_tests -q
uv run ruff format packages/pyd3js-delaunay
uv run ruff check packages/pyd3js-delaunay
uv run ty check packages/pyd3js-delaunay

Coverage (optional)

uv run pytest packages/pyd3js-delaunay/package_tests --cov=pyd3js_delaunay --cov-report=term-missing

Build

uv build packages/pyd3js-delaunay

README and user guide Python snippets are checked by package_tests/test_delaunay_docs_examples.py.

Releasing (PyPI)

1. Ensure dylaunator 0.1.0 is published (this package pins it exactly).
2. From the monorepo root:

uv build packages/pyd3js-delaunay

Upload dist/pyd3js_delaunay-*.whl and dist/pyd3js_delaunay-*.tar.gz (for example with twine upload or uv publish). Bump version in pyproject.toml and add a section here before each new release.

License

ISC — see LICENSE.