We develop a set of Python packages to provide a modern programming interface to codes used for analysis of nuclear reactors. Currently implemented interfaces to the Monte Carlo (MC) neutronics code MCNP and thermo-hydraulic (TH) code SCF allow efficient description of calculation models and provide a framework for coupled calculations. In this paper we illustrate how these interfaces can be used to describe a pin model, and report results of coupled MCNP-SCF calculations performed for a PWR fuel assembly, organized by means of the interfaces
