scipy.sparse
scipy.sparse.dok_matrix.nnz
scipy.sparse.dok_matrix.asfptype
dok_matrix.
asformat
Return this matrix in a given sparse format
format : {string, None}
desired sparse matrix format None for no format conversion “csr” for csr_matrix format “csc” for csc_matrix format “lil” for lil_matrix format “dok” for dok_matrix format and so on