np.expand_dims的用法
np.expand_dims（a，axis=？）
即扩展维度，np.expand_dims(a,axis=)即在 a 的相应的axis轴上扩展维度
a = np.array([[1,2],[3,5]])
y = np.expand_dims(a, axis=2)
z = np.expand_dims(a, axis=1)
print(a.shape)
print(y.shape)
print(z.shape)
输出
(2, 2)
(2, 2, 1)
(2, 1, 2)
y 变成了 [
[ [1], [2] ],
[ [3], [5] ]
]
z 变成了[
[ [1,2],[3,5] ]
]