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Anywidget demo: drawdata

drawdata is a small anywidget — a self-contained ES module that draws onto a <canvas>. Click and drag in the panel below to scribble points; press a number key (1–4) before drawing to switch the active class.

This page is static — there is no Python kernel running. The widget renders because marimo-book extracts the inlined ES module from marimo export's output and mounts it via a ~150-line shim (marimo_book.js). See Anywidgets for the full pipeline.

canvas = mo.ui.anywidget(ScatterWidget(height=320))
canvas

What you can and can't do statically

  • ✅ The widget renders — anywidget's _esm trait is inlined as a data: URL, so no kernel and no CDN are required.
  • ✅ All client-side interaction works — drawing, brush colours, the canvas itself.
  • ❌ The drawn data cannot flow into a downstream Python cell. That needs a kernel.

For genuine Python reactivity (drawn points → live DataFrame → live plot) flip the chapter to mode: wasm in book.yml. See the WASM demo for what that looks like.