  The dual fermion method is a multiscale approach for solving lattice problems
of interacting strongly correlated systems. In this paper, we present the
\texttt{opendf} code, an open-source implementation of the dual fermion method
applicable to fermionic single-orbital lattice models in dimensions $D=1,2,3$
and $4$. The method is built on a dynamical mean field starting point, which
neglects all local correlations, and perturbatively adds spatial correlations.
Our code is distributed as an open-source package under the GNU public license
version 2.
