[nneonneo]

Have you ever tried appending to a NumPy array in a loop? It's a total disaster! And dtype=object arrays are mostly useless; they gain almost none of the benefits of regular NumPy (you may as well run np functions on plain lists) and play poorly with other types. NumPy is great for numerics and structured data - lists are general purpose structures for data manipulation. They are different, have different goals and trade offs, and I don't think it's appropriate to claim that one size should fit all.