Python中数组,列表:冒号的灵活用法介绍(np数组,列表倒序)

import numpy as np
x=np.array([[1,2,3],[5,6,7],[7,8,9]])
print(x)
Out[64]:
array([[1, 2, 3],
  [5, 6, 7],
  [7, 8, 9]])

print(x[:,::-1])
Out[65]:
[[3 2 1]
 [7 6 5]
 [9 8 7]]

x=np.array([[1,2,3],[5,6,7],[7,8,9]])
print(x)
print('------------')
print(x[:,::-1])
print('------------')
print(x[:,::1])
print('------------')
print(x[:,::2])
print('------------')
print(x[:,::3])
print('------------')
print(x[:,::666666])
x=np.array([[1,2,3],[5,6,7],[7,8,9]])
print(x)
print('------------')
print(x[:,::-1])
print('------------')
print(x[:,::1])
print('------------')
print(x[:,::2])
print('------------')
print(x[:,::3])
print('------------')
print(x[:,::666666])
[[1 2 3]
 [5 6 7]
 [7 8 9]]
------------
[[3 2 1]
 [7 6 5]
 [9 8 7]]
------------
[[1 2 3]
 [5 6 7]
 [7 8 9]]
------------
[[1 3]
 [5 7]
 [7 9]]
------------
[[1]
 [5]
 [7]]
------------
[[1]
 [5]
 [7]]