This program is quick & lazy but it uses a 1D python list and pretends it's a 2D list. It implements 2D slicing, giving you a square subset just like ndarray. It doesn't intend to be all correct or nice or useful.

https://www.pythonmorsels.com/p/2rk5t/

Is laziness a virtue? I reused the slicing implementation in `range(foo)[index]` so I didn't need to do that logic myself.