pyd3js-dispatch

Python port of d3-dispatch.

Tracked version: see upstream_lock.json.

What is a dispatch?

A dispatch is a small, namespaced event-listener registry. You create it with a fixed set of event types (e.g. "start", "end"), attach callbacks via .on("type.namespace", fn), and later trigger all callbacks of a type via .call("type", that, *args) / .apply("type", that, args).

This pattern is used throughout D3 to provide internal events (drag/zoom/brush/transition, etc.) without requiring a DOM or a heavyweight event system.

What you get

• Upstream export parity (for the pinned d3-dispatch@3.0.1): the compatibility matrix below covers every upstream export; nothing is marked [missing].
• 100% Python test coverage for pyd3js_dispatch (run the coverage command below).

Install

From PyPI:

pip install pyd3js-dispatch

This repo is a uv workspace monorepo. For local development:

uv sync --group dev

Usage

import pyd3js_dispatch as dd

d = dd.dispatch("start", "end")
log: list[tuple[str, int]] = []

d.on("start.foo", lambda this, x: log.append(("foo", x)))
d.call("start", None, 1)
print(log)

d.on("start.foo", None)
d.call("start", None, 2)
print(log)

[('foo', 1)]
[('foo', 1)]

Compatibility matrix (pinned upstream)

• dispatch — [unit]

Development

Coverage:

uv run pytest packages/pyd3js-dispatch/tests --cov=pyd3js_dispatch --cov-report=term-missing