Format on save for a notebook

Formatting with ‘Format Cell’ and ‘Format Notebook’ works but saving a notebook does not apply the formatters to each cell like a normal file would.

Example notebook cell that would be formatted if it was python:

\





print("hello, world")

# output


print("hello, world")

[NickCrews]

I’d also love format on save for notebooks. As mentioned above, I can use black **/*.ipynb and it works great (you need to install black with the jupyter extra, eg as python -m pip install black[jupyter]), but I’m now just banging my head against the wall trying to get this to run automatically…

[janosh]

@NickCrews There is "editor.codeActionsOnSave" but it doesn’t allow running arbitrary shell commands (for security reasons?) so you’d need to install an extension like Run On Save and get it call to black path/to/file.ipynb on save events.

Sadly even that doesn’t work atm since VS Code does not yet expose lifecycle events for notebooks. The issues to upvote for that are

• https://github.com/emeraldwalk/vscode-runonsave/issues/57
• https://github.com/microsoft/vscode/issues/130799

If both get implemented, you should be able to add this to your settings to auto-format Jupyter notebooks:

"emeraldwalk.runonsave": {
  "commands": [
    {
      "match": "\\.ipynb$",
      "cmd": "black ${file}"
    }
  ]
}