NumPy 高级索引

import numpy as np 
x = np.array([[1,  2],  [3,  4],  [5,  6]]) 
y = x[[0,1,2],  [0,1,0]]  
print (y)

[1  4  5]

import numpy as np 
x = np.array([[  0,  1,  2],[  3,  4,  5],[  6,  7,  8],[  9,  10,  11]])  
print ('我们的数组是：' )
print (x)
print ('\n')
rows = np.array([[0,0],[3,3]]) 
cols = np.array([[0,2],[0,2]]) 
y = x[rows,cols]  
print  ('这个数组的四个角元素是：')
print (y)

我们的数组是：
[[ 0  1  2]
 [ 3  4  5]
 [ 6  7  8]
 [ 9 10 11]]


这个数组的四个角元素是：
[[ 0  2]
 [ 9 11]]

import numpy as np

a = np.array([[1,2,3], [4,5,6],[7,8,9]])
b = a[1:3, 1:3]
c = a[1:3,[1,2]]
d = a[...,1:]
print(b)
print(c)
print(d)

[[5 6]
 [8 9]]
[[5 6]
 [8 9]]
[[2 3]
 [5 6]
 [8 9]]

import numpy as np
x = np.array([[0, 1, 2], [3, 4, 5], [6, 7, 8], [9, 10, 11]])
print('当前数组是：')
print(x)
# 现在我们会打印出大于 5 的元素
print('大于 5 的元素是：')
print(x[x > 5])

import numpy as np 

a = np.array([np.nan,  1,2,np.nan,3,4,5])  
print (a[~np.isnan(a)])

[ 1.   2.   3.   4.   5.]

import numpy as np 

a = np.array([1,  2+6j,  5,  3.5+5j])  
print (a[np.iscomplex(a)])

[2.0+6.j  3.5+5.j]

import numpy as np 

x=np.arange(32).reshape((8,4))
print (x[[4,2,1,7]])

[[16 17 18 19]
 [ 8  9 10 11]
 [ 4  5  6  7]
 [28 29 30 31]]

import numpy as np 

x=np.arange(32).reshape((8,4))
print (x[[-4,-2,-1,-7]])

[[16 17 18 19]
 [24 25 26 27]
 [28 29 30 31]
 [ 4  5  6  7]]

import numpy as np 

x=np.arange(32).reshape((8,4))
print (x[np.ix_([1,5,7,2],[0,3,1,2])])

[[ 4  7  5  6]
 [20 23 21 22]
 [28 31 29 30]
 [ 8 11  9 10]]