使用append函数将一个二维数组添加到一个空数组，关键是维度要对的上

a=np.empty([0,3])
b = np.array([[1,2,3],[4,5,6]])
c=[[7,8,9]]
 
print(a.shape)
print(b.shape)
 
 
a = np.append(a, b, axis=0)
 
a = np.append(a, c, axis=0)
 
print(a.shape)
print(b.shape)