Here is a google colab notebook that runs you through the basics of using colab notebooks:
https://colab.research.google.com/notebooks/basic_features_overview.ipynb
This one is a comprehensive basic python tutorial. One can learn python without reading a book, or even installing python on your own system (good for someone who knows basic programming, but not python language).
https://colab.research.google.com/github/cs231n/cs231n.github.io/blob/master/python-colab.ipynb
Maybe the most impressive thing you can run on google colab now is the AlphaFold2 code, fold any protein for free.
https://colab.research.google.com/github/deepmind/alphafold/blob/main/notebooks/AlphaFold.ipynb
linkstream2 microblog 