element-51

Design node-editor GUIs from Python. You write nodes as typed functions or small classes. element-51 serves an editor in the browser where people wire them together, and Python keeps the graph, runs it and can change it while the page is open.

• Nodes from type hints. Put @element_51.node on a function, or subclass element_51.Node. Parameters become inputs and the return type becomes the output (a pydantic model gives one output per field).
• A fast editor. The canvas is drawn by a Rust and WebAssembly module: pan, zoom, drag, link, undo and redo, typed values in the node, a nested add-node menu with search, and refused links between ports of different types.
• Python is in charge. The graph lives in your process. Read it, run it, save and load it as JSON, or add nodes from a script and watch an open page update.
• Yours to restyle. Three themes ship, and a small JSON file changes any colour, size, font or port shape.
• Embeddable. It is an ASGI app, so it mounts inside FastAPI, NiceGUI or any other ASGI host.

Installation

uv add element-51

To work on it from a clone, you also need Rust (the stable toolchain from rustup, with the wasm32-unknown-unknown target) to build the browser layer:

uv sync
uv run python tools/build_wasm.py

Example

Two nodes and a link. number is a function, Double is a class.

import element_51


@element_51.node
def number() -> float:
    return 21.0


class Double(element_51.Node):
    value: float = 0.0

    def run(self) -> float:
        return self.value * 2


app = element_51.App([number, Double])
first = app.add_node(number, x=60, y=80)
second = app.add_node(Double, x=320, y=80)
app.add_link(first, "out", second, "value")
element_51.serve(app, open_browser=True)

Run it and your browser opens on the editor. Press Run: number shows 21.0 and Double shows 42.0. Right-click the canvas to add more nodes. Stop the server with Ctrl+C.

More examples, grouped by topic, are in examples/: the basics, node types, using the graph from plain Python, editor features, themes, and embedding the editor in FastAPI or NiceGUI.

Looks

The header shows the purple-synthwave theme, the default. The dark antimony theme is one argument away (serve(app, theme="antimony")):

The light theme is one argument away (serve(app, theme="antimony-light")):

purple-synthwave was made from a Coolors palette. Paste any palette link into the editor's menu and it takes the colours at once, keeping the text readable (examples/e_look/e3_palette.py).

Documentation

The documentation has the guides and the API reference (the sources are in docs/). To build it, run uv sync --group docs and then uv run sphinx-build -b html docs docs/_build/html.

Credits

The look of the editor is inspired by Antimony, the graph-based CAD tool by Matt Keeter. element-51 shares no code or images with Antimony; the colours, shapes and layout were drawn again from scratch.