Numpy Array Indexing and Selection Now that we know how to build arrays, let's look at how to pull values our of an array using indexing, and also slicing off sections of an array. Indexing This is ...

x = np.array([_ for _ in range(1000)]) This works, but its performance is hidebound by the time it takes for Python to create a list, and for NumPy to convert that list into an array.