Numpy find index in a list of arrays appeared in another list of arrays-CodePudding

So suppose I have a list of arrays called original_arr, another list of arrays called find_arr,how can I find the index of elements of original_arr appeared in find_arr? (I have many number of lists to deal with)

a = np.arange(27).reshape(9,3)
original_arr = np.split(a,3)
>>> original_arr
>>> [array([[0, 1, 2],
            [3, 4, 5],
            [6, 7, 8]]), 
     array([[ 9, 10, 11],
            [12, 13, 14],
            [15, 16, 17]]), 
     array([[18, 19, 20],
            [21, 22, 23],
            [24, 25, 26]])]

b = np.array([[0,1,2],[3,4,5],[12,13,14],[15,16,17],[21,22,23]])
find_arr =  np.split(b,np.array([2,2,1]).cumsum()[:-1])
>>> find_arr
>>> [array([[0, 1, 2],
            [3, 4, 5]]), 
     array([[12, 13, 14],
            [15, 16, 17]]), 
     array([[21, 22, 23]])]

so I tried the code below, but it doesn't work

index = np.empty((0,2),int)

for i in range (len(find_arr)):
    for j in range (len(find_arr[i])):
        m = np.where((original_arr[i] == find_arr[i][j]).all(axis=1))
        index = np.append(index,m,axis=0)

what I expect the output is to be (for example. because [0, 1, 2] in find_arr appears in original_arr[0][0], so the output should be [0,0] or [[0],[0]]) :

array[[[0,0],[0,1]],
      [[1,1],[1,2]],
      [[2,1]]]

or 
array[[[[0],[0]],[[0],[1]]],
      [[[1],[1]],[[1],[2]]],
      [[[2],[1]]]]

can anybody check where my code is wrong? or is there any easier way to do this?

CodePudding user response：

You want to append the row number, i, to m, but m has different type. So take the output from np.where(..)[0][0] as below and append it to i before inserting into index.

for i in range (len(find_arr)):
    for j in range (len(find_arr[i])):
        m = np.where((original_arr[i] == find_arr[i][j]))[0][0]
        index = np.append(index,[[i, m]],axis=0)

Another option, which might be a bit faster, is to use np.nonzero(..==..)[0][0] like this:

m = np.nonzero((original_arr[i] == find_arr[i][j]))[0][0]

Both of which will output:

[[0 0]
 [0 1]
 [1 1]
 [1 2]
 [2 1]]

as you would expect.