Abstract
<jats:p>Commercial quantum chemistry packages operate as opaque black boxes for most students. We present physcode, an open-source Python pedagogical interface built around PySCF that reads standard Gaussian-format .gjf input and writes Gaussian-compatible .log output readable by Chemcraft and Avogadro. physcode contributes a Gaussian-style parser, a method dispatcher, a formatted log writer, plotting utilities, and student-modifiable code hooks that expose the SCF cycle, Hessian construction, and excited-state calculations in readable Python. It supports a progression from Hartree–Fock through DFT, MP2, coupled cluster, and TD-DFT/CIS, together with IR/Raman spectra and a ro-vibrational band simulator. physcode has been used in an advanced undergraduate and graduate computational chemistry laboratory at the Universitat de Barcelona over two academic years (n = 28 students). Exit-question scores were higher in the physcode cohort than in a historical Gaussian-only comparison cohort (n = 12), though the non-randomized design limits causal inference. Complete source code, annotated example inputs, student worksheets, and an instructor guide are provided as Supporting Information.</jats:p>