获取非null稀疏csr矩阵行的索引

Question

I want to get the indices of the rows of a scipy.sparse.csr_matrix that are not null. For example:

A = [ 0 0 0 0 0 1
      0 0 0 0 0 0 
      1 1 0 0 0 0 ]

Desired output:

indices = [0, 2]

Answer 1

Code:

from scipy.sparse import find, csr_matrix
import numpy as np

A = csr_matrix(np.array([[0, 0, 0, 0, 0, 1], [0, 0, 0, 0, 0, 0], [1, 1, 0, 0, 0, 0]]))
print(A.todense())

nnz_per_row = A.getnnz(axis=1)
result = np.where(nnz_per_row > 0)[0]

print(result)

Output:

[[0 0 0 0 0 1]
 [0 0 0 0 0 0]
 [1 1 0 0 0 0]]
[0 2]