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No error is raised. playground.py opens as a plain Python file with # %% markers instead of notebook cells. Playgrounds use jupytext percent format: one .py file that behaves as a notebook in the right editor.

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Fix

  • VS Code: install the Python extension, then open playground.py and use Run Cell / the interactive window. VS Code understands # %% natively.
  • JupyterLab: enable the jupytext contents manager so percent-format files open as notebooks.
  • Committed an .ipynb by accident: the repo keeps playgrounds as percent-format Python. In a repository checkout, run bake nb-to-py to convert everything back and delete the .ipynb files.
How the playground is meant to be used is covered in Notebooks. Not this problem? Every fix lives on Troubleshooting.
Last modified on August 31, 2026