arrays - 在numpy中转置矩阵

Question

我有这个 numpy 数组:

a = np.array([[[1,2,3],[-1,-2,-3]],[[4,5,6],[-4,-5,-6]]])

b是 a 的转置.我希望 b 是这样的:

b = np.array([[[1,-1],[2,-2],[3,-3]],[[4,-4],[5,-5],[6,-6]]])

是否可以在一行中完成？

编辑:

如果我有这个:

a = np.empty(3,dtype = object)

a[0] = np.array([[1,2,3],[-1,-2,-3]])

a[1] = np.array([[4,5,6],[-4,-5,-6]])

我怎样才能得到b？

Answer 1

你可以使用 np.transpose(a,(0,2,1)) :

In [26]: a = np.array([[[1,2,3],[-1,-2,-3]],[[4,5,6],[-4,-5,-6]]])

In [27]: b = np.transpose(a,(0,2,1))

In [28]: print a
[[[ 1  2  3]
  [-1 -2 -3]]

 [[ 4  5  6]
  [-4 -5 -6]]]

In [29]: print b
[[[ 1 -1]
  [ 2 -2]
  [ 3 -3]]

 [[ 4 -4]
  [ 5 -5]
  [ 6 -6]]]

对于您编辑的问题，数组为 dtype=object -- 没有直接的方法来计算转置，因为 numpy 不知道如何转置通用对象。但是，您可以使用列表理解并分别转置每个对象:

In [90]: a = np.empty(2,dtype = object)

In [91]: a[0] = np.array([[1,2,3],[-1,-2,-3]])

In [92]: a[1] = np.array([[4,5,6],[-4,-5,-6]])

In [93]: print a
[[[ 1  2  3]
 [-1 -2 -3]] [[ 4  5  6]
 [-4 -5 -6]]]

In [94]: b = np.array([np.transpose(o) for o in a],dtype=object)

In [95]: print b
[[[ 1 -1]
  [ 2 -2]
  [ 3 -3]]

 [[ 4 -4]
  [ 5 -5]
  [ 6 -6]]]