import numpy as np
from scipy import sparse

# dense matrix
A = np.array([[1,2,0],[0,0,3],[1,0,4]])
# sparse matrix
sA = sparse.csr_matrix(A)

# print dense matrix
print(A)

[[1 2 0]
[0 0 3]
[1 0 4]]

# print sparse matrix
print(sA)

(0, 0) 1
(0, 1) 2
(1, 2) 3
(2, 0) 1
(2, 2) 4

# sparse 转为 dense
sA.todense()

matrix([[1, 2, 0],
[0, 0, 3],
[1, 0, 4]], dtype=int64)