About LU factorization

[salvomic]

Given the permutation matrix (by LU), like [1,3,2] is there a way to obtain the actual permutation matrix (like P21 = [[0,1,0], [1,0,0], [0,0,1]] ?
I need to make a routine with that matrix for the program to calculate LDU factorization as, sometime, L*D*U returns the matrix A with some swap of rows (indicated by the permutation matrix by LU).

Salvo