numpy create array of the max of consecutive pairs in another array

Question

I have a numpy array:

A = np.array([8, 2, 33, 4, 3, 6])

What I want is to create another array B where each element is the pairwise max of 2 consecutive pairs in A, so I get:

B = np.array([8, 33, 33, 4, 6])

Any ideas on how to implement?
Any ideas on how to implement this for more then 2 elements? (same thing but for consecutive n elements)

Edit:

The answers gave me a way to solve this question, but for the n-size window case, is there a more efficient way that does not require loops?

Edit2:

Turns out that the question is equivalent for asking how to perform 1d max-pooling of a list with a window of size n. Does anyone know how to implement this efficiently?

Answer 1

One solution to the pairwise problem is using the np.maximum function and array slicing:

B = np.maximum(A[:-1], A[1:])

Answer 2

A loop-free solution is to use max on the windows created by skimage.util.view_as_windows:

list(map(max, view_as_windows(A, (2,))))

[8, 33, 33, 4, 6]

Copy/pastable example:

import numpy as np
from skimage.util import view_as_windows

A = np.array([8, 2, 33, 4, 3, 6])

list(map(max, view_as_windows(A, (2,))))