Help me understand a simple list comprehension

[PiPy]

Thanks buran, for the additional information you provided...very helpful (and interesting to learn) indeed!

Your explanation brings up another question/clarification though i.e. when would I use one, over the other i.e. numpy ndarray object vs python list object?

Thanks also for clarifying re. the 2D array. I realize that there is no depth (3rd dimension) involved.