Create 3D array using Python

Solution 1:

You should use a list comprehension:

>>> import pprint
>>> n = 3
>>> distance = [[[0 for k in xrange(n)] for j in xrange(n)] for i in xrange(n)]
>>> pprint.pprint(distance)
[[[0, 0, 0], [0, 0, 0], [0, 0, 0]],
 [[0, 0, 0], [0, 0, 0], [0, 0, 0]],
 [[0, 0, 0], [0, 0, 0], [0, 0, 0]]]
>>> distance[0][1]
[0, 0, 0]
>>> distance[0][1][2]
0

You could have produced a data structure with a statement that looked like the one you tried, but it would have had side effects since the inner lists are copy-by-reference:

>>> distance=[[[0]*n]*n]*n
>>> pprint.pprint(distance)
[[[0, 0, 0], [0, 0, 0], [0, 0, 0]],
 [[0, 0, 0], [0, 0, 0], [0, 0, 0]],
 [[0, 0, 0], [0, 0, 0], [0, 0, 0]]]
>>> distance[0][0][0] = 1
>>> pprint.pprint(distance)
[[[1, 0, 0], [1, 0, 0], [1, 0, 0]],
 [[1, 0, 0], [1, 0, 0], [1, 0, 0]],
 [[1, 0, 0], [1, 0, 0], [1, 0, 0]]]

Solution 2:

numpy.arrays are designed just for this case:

 numpy.zeros((i,j,k))

will give you an array of dimensions ijk, filled with zeroes.

depending what you need it for, numpy may be the right library for your needs.

Solution 3:

The right way would be

[[[0 for _ in range(n)] for _ in range(n)] for _ in range(n)]

(What you're trying to do should be written like (for NxNxN)

[[[0]*n]*n]*n

but that is not correct, see @Adaman comment why).

Solution 4:

d3 = [[[0 for col in range(4)]for row in range(4)] for x in range(6)]

d3[1][2][1]  = 144

d3[4][3][0]  = 3.12

for x in range(len(d3)):
    print d3[x]



[[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]]
[[0, 0, 0, 0], [0, 0, 0, 0], [0, 144, 0, 0], [0, 0, 0, 0]]
[[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]]
[[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]]
[[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [3.12, 0, 0, 0]]
[[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]]

Solution 5:

"""
Create 3D array for given dimensions - (x, y, z)

@author: Naimish Agarwal
"""


def three_d_array(value, *dim):
    """
    Create 3D-array
    :param dim: a tuple of dimensions - (x, y, z)
    :param value: value with which 3D-array is to be filled
    :return: 3D-array
    """

    return [[[value for _ in xrange(dim[2])] for _ in xrange(dim[1])] for _ in xrange(dim[0])]

if __name__ == "__main__":
    array = three_d_array(False, *(2, 3, 1))
    x = len(array)
    y = len(array[0])
    z = len(array[0][0])
    print x, y, z

    array[0][0][0] = True
    array[1][1][0] = True

    print array

Prefer to use numpy.ndarray for multi-dimensional arrays.