python - Get rows of a first array matching rows of a second one -

suppose have array a of shape (m, k) , b of shape (n, k).

the rows of b possible patterns can encountered (each pattern 1d array of size k).

i array c of shape (m,) c[i] indice of pattern (in b) of row i in a.

i doing in loop (i.e. looping on possible patterns) end using vectorization.

here example:

a = np.array([[0, 1], [0, 1], [1, 0]]) b = np.array([[0, 0], [0, 1], [1, 0], [1, 1]]) 

i expecting:

c = np.array([1, 1, 2]) 

based on this solution, here's vectorized solution using np.searchsorted -

dims = b.max(0)+1 a1d = np.ravel_multi_index(a.t,dims) b1d = np.ravel_multi_index(b.t,dims) sidx = b1d.argsort() out = sidx[np.searchsorted(b1d,a1d,sorter=sidx)] 

sample run -

in [43]: out[43]:  array([[72, 89, 75],        [72, 89, 75],        [93, 38, 61],        [47, 67, 50],        [47, 67, 50],        [93, 38, 61],        [72, 89, 75]])  in [44]: b out[44]:  array([[47, 67, 50],        [93, 38, 61],        [41, 55, 27],        [72, 89, 75]])  in [45]: out out[45]: array([3, 3, 1, 0, 0, 1, 3])