python中[-1]、[:-1]、[::-1]、[n::-1]的用法

import numpy as np



a=np.random.rand(5)
print(a)
[ 0.64061262  0.8451399   0.965673    0.89256687  0.48518743]

print(a[-1]) # 取最后一个元素
[0.48518743]

print(a[:-1])  # 除了最后一个取全部
[ 0.64061262  0.8451399   0.965673    0.89256687]

print(a[::-1]) # 取从后向前（相反）的元素
[ 0.48518743  0.89256687  0.965673    0.8451399   0.64061262]

print(a[2::-1]) # 取从下标为2的元素翻转读取
[ 0.965673  0.8451399   0.64061262]