On the other hand, whenever I see Python code that does calculations over arrays of data with nested loops instead of using numpy, it always takes me a distress

On the other hand, whenever I see Python code that does calculations over arrays of data with nested loops instead of using numpy, it always takes me a distressing amount of time to see what the code is actually doing and that the bug is because of a typo buried deep in that 100 lines of code that caused one of the inner products to be incorrect.