02.Fancy Indexing

import numpy as np
x = np.arange(16)

index = [3,5,8]
x[index]

array([3, 5, 8])

X = x.reshape(4,-1)
X

array([[ 0,  1,  2,  3],
       [ 4,  5,  6,  7],
       [ 8,  9, 10, 11],
       [12, 13, 14, 15]])

row = np.array([0,1,2])
col = np.array([1,2,3])
X[row,col]

array([ 1,  6, 11])

col = [True,False,True,True]
X[col]

array([[ 0,  1,  2,  3],
       [ 8,  9, 10, 11],
       [12, 13, 14, 15]])