Numpy 笔记

增加矢量维度：

1. 用None作为索引

a = np.array([1,2,3])        #a.shape = (3,)
a = a[None, :]               #a.shape = (1,3)

2. np.newaxis

a = np.array([1,2,3])        #a.shape = (3,)
a = a[np.newaxis, :]         #a.shape = (1,3)

3. reshape

a = np.array([1,2,3])                    #a.shape = (3,)
a = np.reshape(a, ((1,)+a.shape))        #a.shape=(1,3)
或a.reshape(((1,)+a.shape))