python list [:1]

python 切片slice

 1、补充：

A = np.ones([2, 3, 4])

B = np.ones([2, 4])

C = A*B[:, None, :]

C.shape = 2,1,4

https://www.liaoxuefeng.com/wiki/001374738125095c955c1e6d8bb493182103fac9270762a000/0013868196352269f28f1f00aee485ea27e3c4e47f12bc7000