Implementation of Lanczos method that returns tridiagonal matrix

Question

The Lanczos method can be used to obtain extremal eigenpairs of sparse symmetric or hermitian matrices. I know there are several implementations of the Lanczos method (as well as Arnoldi, Davidson, and others) out there, but I am specifically interested in one that returns the tridiagonal matrix, not just the eigenvalues and eigenvectors. The way I am doing this now is using my own Lanczos implementation in Fortran. Is there a maintained library that does the same efficiently, preferably in python?