Code formatter like nb_black for google colab

Question

I know that for jupyter notebooks and jupyter lab, there are available code formatter extensions such as nb_blackor blackcellmagic. However when I installed them, it doesn't seem to work on google colab.

Do you know if there are any native option in colab or an extension that formats code (pep8 compliant)?

Answer 1

As of now (April 2023) the top answer - black - works without kernel restarts.

So

# run once
!pip install black[jupyter] --quiet
from google.colab import drive
drive.mount("/content/drive")
...
# run many times
!black /content/drive/MyDrive/'Colab Notebooks'/'HiringBias.ipynb'

plus page refreshing gives

reformatted /content/drive/MyDrive/Colab Notebooks/HiringBias.ipynb
All done! ✨  ✨
1 file reformatted.

:-)

Answer 2

I don't think there's an extension directly in Colab.

What you could do, though, is to download your notebook, run

pip install -U nbqa
nbqa black notebook.ipynb

and then reupload your (now formatted) notebook to Colab

---

disclaimer: I'm the author of nbQA

---

UPDATE: as of version 21.8b0, black runs directly on notebooks, no third-party tool required

Answer 3

I have tried everything, none of the JupyterLab/Notebook backend hack methods seem to work as of February 2022. However, until later here is a relatively simple workaround:

[Run only once, at startup]

• Connect to your drive

  from google.colab import drive
drive.mount("/content/drive")

• Install black for jupyter

  !pip install black[jupyter]

• Restart kernel

[Then]

• Place your .ipynb file somewhere on your drive
• Anytime you want format your code run:
  !black /content/drive/MyDrive/YOUR_PATH/YOUR_NOTEBOOK.ipynb
• Don't save your notebook, hit F5 to refresh the page
• Voila!
• Now save!