python - How do I group elements of a numpy array by two? -

i facing following problem. have np.array, of following structure:

[a, b, c, d, e, f] 

where a..f numpy arrays, guaranteed of same size. hoping achieve following shape:

[ | b, c | d, e | f ] 

where a | b np.hstack([a, b]). able generalize number of elements in hstack, given number divides length of array.

i not sure how achieve - there nice solution, experience doesn't lead me there. appreciate insight.

a manual way compose numpy array out of smaller blocks use np.block or np.bmat:

h, w, n = 3, 4, 6 a, b, c, d, e, f = [np.full((h,w), i) in list('abcdef')] result = np.block([[a, b], [c, d], [e, f]]) 

yields

array([['a', 'a', 'a', 'a', 'b', 'b', 'b', 'b'],        ['a', 'a', 'a', 'a', 'b', 'b', 'b', 'b'],        ['a', 'a', 'a', 'a', 'b', 'b', 'b', 'b'],        ['c', 'c', 'c', 'c', 'd', 'd', 'd', 'd'],        ['c', 'c', 'c', 'c', 'd', 'd', 'd', 'd'],        ['c', 'c', 'c', 'c', 'd', 'd', 'd', 'd'],        ['e', 'e', 'e', 'e', 'f', 'f', 'f', 'f'],        ['e', 'e', 'e', 'e', 'f', 'f', 'f', 'f'],        ['e', 'e', 'e', 'e', 'f', 'f', 'f', 'f']],       dtype='<u1') 

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assuming blocks 2d arrays, more automated way reshape numpy array of blocks use unblockshaped:

import numpy np  def unblockshaped(arr, h, w):     """     http://stackoverflow.com/a/16873755/190597 (unutbu)     return array of shape (h, w)     h * w = arr.size      if arr of shape (n, nrows, ncols), n sublocks of shape (nrows, ncols),     returned array preserves "physical" layout of sublocks.     """     n, nrows, ncols = arr.shape     return (arr.reshape(h // nrows, -1, nrows, ncols)                .swapaxes(1, 2)                .reshape(h, w))  h, w, n = 3, 4, 6 arr = np.array([np.full((h,w), i) in list('abcdef')]) result = unblockshaped(arr, h*n//2, w*2) print(result) 

which produces same result.

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see this question example of how arrange sequence of images grid.