sparse 3d matrix/array in Python?

Question

In scipy, we can construct a sparse matrix using scipy.sparse.lil_matrix() etc. But the matrix is in 2d.

I am wondering if there is an existing data structure for sp

Answer 1

An alternative answer as of 2017 is the sparse package. According to the package itself it implements sparse multidimensional arrays on top of NumPy and scipy.sparse by generalizing the scipy.sparse.coo_matrix layout.

Here's an example taken from the docs:

import numpy as np
n = 1000
ndims = 4
nnz = 1000000
coords = np.random.randint(0, n - 1, size=(ndims, nnz))
data = np.random.random(nnz)

import sparse
x = sparse.COO(coords, data, shape=((n,) * ndims))
x
# 

x.nbytes
# 16000000

y = sparse.tensordot(x, x, axes=((3, 0), (1, 2)))

y
#