None起到的是增加维度的作用。 示例如下:
import numpy as np z = np.ones((3, 3, 3)) print(z.shape) # (3,3,3) print(z[:, None, None].shape) # (3,1,1,3,3) print(z[:, None, :].shape) # (3,1,3,3) print(z[None, :].shape) # (1,3,3,3) print(z[:, None].shape) # (3,1,3,3)