easydot 0.1.8

Tiny browser-side Graphviz DOT rendering helpers for notebooks and web views

easydot

Graphviz in the browser. Zero installs. One line of Python.

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Browser notebooks can run JavaScript and WebAssembly, but they can't import arbitrary files from Python site-packages. Embedding the full Graphviz WASM bundle in every cell bloats your notebook. Loading from a CDN on every render breaks offline and locked-down environments.

easydot takes the middle path: it vendors Graphviz WASM, starts a tiny loopback asset server on demand, and lets notebook outputs reference a local URL. Small outputs. No manual setup. Works offline.

Quick Start

uv add easydot

import easydot

easydot.display("digraph { A -> B -> C }")

That's it. The return value has _repr_html_() and _mime_() methods, so it renders automatically as the last expression in a notebook cell.

Source Modes

By default, easydot tries the local server first and falls back to a pinned CDN URL:

easydot.display("digraph { A -> B }", source="auto")   # default
easydot.display("digraph { A -> B }", source="local")  # local only
easydot.display("digraph { A -> B }", source="cdn")    # CDN only

Mode	Local server	CDN fallback	Best for
auto	yes	yes	Most setups
local	yes	no	Air-gapped / offline environments
cdn	no	yes	Remote hosts where 127.0.0.1 isn't reachable from the browser

To change the notebook-wide default without editing every display call, set EASYDOT_SOURCE before rendering any graphs:

import os

os.environ["EASYDOT_SOURCE"] = "cdn"

The environment variable accepts auto, local, or cdn. It only applies when source="auto" is used, so explicit source="local" and source="cdn" calls still win.

Some hosted marimo environments protect marimo's generated iframe file URLs. If CDN mode still shows an authorization error, force a self-contained iframe:

import os

os.environ["EASYDOT_SOURCE"] = "cdn"
os.environ["EASYDOT_IFRAME_MODE"] = "srcdoc"

EASYDOT_IFRAME_MODE accepts auto, marimo, or srcdoc.

marimo Support

easydot works with marimo out of the box. It detects marimo and uses its iframe display helper automatically, since marimo doesn't execute arbitrary inline scripts from plain text/html outputs. All source modes work.

Because of that script policy, iframe=False is not a marimo rendering mode. Use it only when embedding the generated HTML somewhere that already provides layout and executes script tags.

To inspect the bundled demo notebook from a checkout:

uv run marimo edit examples/demo.py

For a read-only local preview:

uv run marimo run examples/demo.py --headless --host 127.0.0.1 --port 2718 --no-token

Then open http://localhost:2718.

Library Integration

For libraries that generate their own HTML, use the lower-level asset API:

from easydot import asset_urls

js_url = asset_urls()["js"]

Then in your browser-side code:

const mod = await import(jsUrl);
const graphviz = await mod.Graphviz.load();
const svg = graphviz.layout("digraph { A -> B }", "svg", "dot");

CLI

easydot ships a small command-line tool:

# Render DOT to HTML on stdout
echo 'digraph { A -> B }' | easydot

# Print local asset server URLs
easydot --urls

Runtime Model

The asset server is intentionally narrow:

• Binds only to 127.0.0.1
• Uses an OS-assigned ephemeral port
• Serves only known packaged files (no directory browsing)
• Sets long-lived cache headers
• Shuts down automatically when the Python process exits

What easydot Is Not

easydot does not call the system dot executable. All rendering happens client-side through WebAssembly. For server-side rendering to files, native Graphviz or the graphviz Python package may be a better fit.

Licensing

The Python code is licensed under BSD-3-Clause.

The vendored browser module (src/easydot/assets/index.js) comes from @hpcc-js/wasm-graphviz, licensed under Apache-2.0. The upstream license is included at src/easydot/assets/LICENSE.hpcc-js-wasm; the pinned version lives in src/easydot/_version.py.

Component	License
easydot Python code	BSD-3-Clause
Vendored Graphviz WASM	Apache-2.0