Numpy/Python: Array iteration without for-loop

Question

So it\'s another n-dimensional array question: I want to be able to compare each value in an n-dimensional arrays with its neighbours. For example if a is the array which is

Answer 1

Something like:

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

which returns

array([False, False, False, False,  True, False], dtype=bool

You can specify an axis too for higher dimensions, though as others have said you'll need to handle the edges somehow as the values wrap around (as you can guess from the name)

For a fuller example in 2D:

# generate 2d data
a = np.array((np.random.rand(5,5)) * 10, dtype=np.uint8)

# check all neighbours
for ax in range(len(a.shape)):
    for i in [-1,1]:
        print a == np.roll(a, i, axis=ax)