Simon Willison’s Weblog

Serializing package requirements in marimo notebooks. The latest release of Marimo - a reactive alternative to Jupyter notebooks - has a very neat new feature enabled by its integration with uv:

One of marimo’s goals is to make notebooks reproducible, down to the packages used in them. To that end, it’s now possible to create marimo notebooks that have their package requirements serialized into them as a top-level comment.

This takes advantage of the PEP 723 inline metadata mechanism, where a code comment at the top of a Python file can list package dependencies (and their versions).

I tried this out by installing marimo using uv:

uv tool install --python=3.12 marimo

Then grabbing one of their example notebooks:

wget 'https://raw.githubusercontent.com/marimo-team/spotlights/main/001-anywidget/tldraw_colorpicker.py'

And running it in a fresh dependency sandbox like this:

marimo run --sandbox tldraw_colorpicker.py

Also neat is that when editing a notebook using marimo edit:

marimo edit --sandbox notebook.py

Just importing a missing package is enough for Marimo to prompt to add that to the dependencies - at which point it automatically adds that package to the comment at the top of the file: