You're partly right. However Python's sweet spot for me is when writing code to process complex, messy, poorly understood data. Using a Jupyter notebook lets me

You're partly right. However Python's sweet spot for me is when writing code to process complex, messy, poorly understood data. Using a Jupyter notebook lets me keep partially processed inputs as live objects, examine and change their in-memory representations, and quickly prototype the next stage of processing. It feels like sculpting with playdoh. Once that's working, the code moves from the Jupyter notebook into a proper code module with unit tests. Then the emphasis is on building the production system rather than manipulating the data. I get what you mean with unit tests. Just for me it feels further away from the data, which is where most the complexity in my business domain lies.