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]