.. _`sec:psithonFunc`: ========================================= Psithon Functions: Invoking a Calculation ========================================= To allow arbitrarily complex computations to be performed, |PSIfour| is built upon the Python interpreter, with modifications termed Psithon. Sec. :ref:`sec:psithonInput` describes the non-standard Python associated with clean molecule, basis, and option specification in the |PSIfour| input file. This documentation addresses the pure Python side- what functions allow the efficient compiled code to be run, what functions post-process and interact with that output, and how the ordinary (or ambitious) user can extent |PSIfours| functionality. .. toctree:: :maxdepth: 2 notes_py energy prop nbody opt freq db cbs diatomic intercalls sowreap cubeprop