Numpy 3d array delete first entry from every row

Question

Let's say I have a 3d Numpy array:

array([[[0, 1, 2],
        [0, 1, 2],
        [0, 2, 5]]])

Is it possible to remove the first entry from all the rows (those inner most rows). In this case the 0 would be deleted in each row.

Giving us the following output:

[[[1, 2],
  [1, 2],
  [2, 5]]]

cs95 · Accepted Answer · 2019-03-02 02:08:01Z

2

x
array([[[0, 1, 2],
        [0, 1, 2],
        [0, 2, 5]]])

x.shape
# (1, 3, 3)

You can use Ellipsis (...) to select across all the outermost axes, and slice out the first value from each row with 1:.

x[..., 1:]    
array([[[1, 2],
        [1, 2],
        [2, 5]]])

x[..., 1:].shape
# (1, 3, 2)

answered Mar 2, 2019 at 1:46

cs95

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2 Comments

Can you explain this syntax?

@JamesMitchell ... means the other axes are not operated on in any way. The 1: indicates to slice the last column in the innermost axis.

jyalim · Accepted Answer · 2019-03-02 04:51:48Z

1

print(x[:,:,1:])
# array([[[1, 2],
#         [1, 2],
#         [2, 5]]])

is equivalent to the established use of the ellipsis.

answered Mar 2, 2019 at 4:51

jyalim

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