Numpy Arrays Basic Ways to Build Arrays. We can cast an ordinary python list as a NumPy one-dimensional array. import numpy as np my_list = [1, 2, 3] np. array (my_list) # cast a list into a 1D array.

As noted above, NumPy arrays behave a lot like other Python objects, for the sake of convenience. For instance, they can be indexed like lists; arr[0] accesses the first element of a NumPy array.

NumPy is known for being fast, but there's always room for improvement. Learn how to use Cython to iterate over NumPy arrays at the speed of C.