Numpy单个元素访问速度比列表慢

I just started using Numpy and noticed that iterating through each element in a Numpy array is ~4x slower than doing the same but with a list of lists. I know now that this defeats the purpose of Numpy and I should vectorize the function if possible. My question is though why is it 4x slower. That seems like quite a large amount.I just started using Numpy and noticed that ite